SLF Data API: integration guide and reference

GET /v1/company

Get your company

Returns the company the key belongs to. Use it to check that your key works and belongs to the company you expect. vat_registered is the VAT setting of your company's profile at SLF, which someone at your company can also change in the client portal. If it is false, every line's vat_category is recorded as none. Every write is refused with 403 forbidden unless this setting and SLF's own record of your company's VAT registration are both set and agree; they can disagree, for example, after the setting is changed in the client portal. Reads, including this one, keep working. Keep the refused records, contact SLF, and send them again once SLF tells you the two agree.

Responses

200 Your company. · Company

{
  "name": "Example Trading Co., Ltd.",
  "name_local": "บริษัท ตัวอย่าง จำกัด",
  "tax_id": "0999000000019",
  "branch_no": "00000",
  "vat_registered": true
}

GET /v1/bank-accounts

List bank accounts

Returns the accounts SLF has on record for your company. Use an account's id as bank_account_id on sales documents, receipts and payments. Only the last four digits of each account number are returned. The list can change between two reads: an account deleted by SLF or in your client portal is no longer listed and its id is gone, and an account edited there keeps its id with the new details. Read the list again before you use an id, and check that bank_name and account_number_last4 still show the account you mean. An id that is no longer listed is refused on writes with 422 reference_not_found.

Parameters

Responses

200 A page of bank accounts. · list of BankAccount

{
  "data": [
    {
      "id": "bnk_5Qm2Rk8Lt3Vw",
      "bank_name": "Example Bank Public Company Limited",
      "account_name": "Example Trading Co., Ltd.",
      "account_number_last4": "4821",
      "currency": "THB",
      "type": null
    },
    {
      "id": "bnk_9Ze3Lp6Qr2Dn",
      "bank_name": "Example Bank Public Company Limited",
      "account_name": "Example Trading Co., Ltd.",
      "account_number_last4": "7730",
      "currency": "USD",
      "type": null
    }
  ],
  "next_cursor": null
}

POST /v1/customers

Create a customer

Creates a customer. Only external_id and name are required. For a customer in Thailand (country TH) with a tax_id, the tax ID's check digit is validated and branch_no defaults to 00000. A customer with the same tax_id and branch_no as an existing one is refused with 409 customer_exists, and existing_id points to the customer already recorded. For a customer outside Thailand, tax_id is optional and its format is not checked.

Parameters

Request body

application/json · Customer

{
  "external_id": "CUST-00412",
  "name": "Sample Retail Co., Ltd.",
  "name_local": "บริษัท ตัวอย่างค้าปลีก จำกัด",
  "country": "TH",
  "tax_id": "0999000000027",
  "branch_no": "00000",
  "address": "88 Example Road, Pathum Wan, Bangkok 10330",
  "email": "accounts@sample-retail.example",
  "phone": "+66 2 000 0000",
  "notes": "Send statements to the accounts team."
}

Responses

201 The customer was created. · Customer

{
  "id": "cus_7Hc4Nf2Pq9Xz",
  "external_id": "CUST-00412",
  "name": "Sample Retail Co., Ltd.",
  "name_local": "บริษัท ตัวอย่างค้าปลีก จำกัด",
  "country": "TH",
  "tax_id": "0999000000027",
  "branch_no": "00000",
  "address": "88 Example Road, Pathum Wan, Bangkok 10330",
  "email": "accounts@sample-retail.example",
  "phone": "+66 2 000 0000",
  "notes": "Send statements to the accounts team.",
  "created_at": "2026-10-15T09:12:44+07:00"
}

409 A customer with this tax_id and branch_no, or this external_id, already exists. · Error

{
  "error": {
    "code": "customer_exists",
    "message": "A customer with tax ID 0999000000027, branch 00000 already exists.",
    "param": "/tax_id",
    "details": [],
    "request_id": "req_7d1a4c8e2f6b9a35",
    "existing_id": "cus_7Hc4Nf2Pq9Xz"
  }
}

422 One or more fields are invalid. · Error

{
  "error": {
    "code": "validation_failed",
    "message": "2 fields are invalid.",
    "param": null,
    "details": [
      {
        "param": "/tax_id",
        "code": "invalid_tax_id",
        "message": "The check digit does not match.",
        "expected": null,
        "received": null
      },
      {
        "param": "/email",
        "code": "invalid_format",
        "message": "Not an email address.",
        "expected": null,
        "received": null
      }
    ],
    "request_id": "req_3c9e1f7a2b5d8c04",
    "existing_id": null
  }
}

Errors specific to this endpoint

duplicate_external_id, customer_exists. Common errors: see Error codes.

GET /v1/customers

List customers

Returns your customers, newest first. Filter by tax ID and branch, or by your own external_id, to find a customer you may have created before.

Parameters

Responses

200 A page of customers. · list of Customer

{
  "data": [
    {
      "id": "cus_3Wd8Lm5Tb2Kr",
      "external_id": "CUST-00977",
      "name": "Example Imports Pte. Ltd.",
      "name_local": null,
      "country": "SG",
      "tax_id": null,
      "branch_no": null,
      "address": "10 Example Street, Singapore 000000",
      "email": "finance@example-imports.example",
      "phone": null,
      "notes": null,
      "created_at": "2026-10-26T16:40:03+07:00"
    },
    {
      "id": "cus_7Hc4Nf2Pq9Xz",
      "external_id": "CUST-00412",
      "name": "Sample Retail Co., Ltd.",
      "name_local": "บริษัท ตัวอย่างค้าปลีก จำกัด",
      "country": "TH",
      "tax_id": "0999000000027",
      "branch_no": "00000",
      "address": "88 Example Road, Pathum Wan, Bangkok 10330",
      "email": "accounts@sample-retail.example",
      "phone": "+66 2 000 0000",
      "notes": "Send statements to the accounts team.",
      "created_at": "2026-10-15T09:12:44+07:00"
    }
  ],
  "next_cursor": null
}

GET /v1/customers/{id}

Get a customer

Returns one customer.

Parameters

Responses

200 The customer. · Customer

{
  "id": "cus_7Hc4Nf2Pq9Xz",
  "external_id": "CUST-00412",
  "name": "Sample Retail Co., Ltd.",
  "name_local": "บริษัท ตัวอย่างค้าปลีก จำกัด",
  "country": "TH",
  "tax_id": "0999000000027",
  "branch_no": "00000",
  "address": "88 Example Road, Pathum Wan, Bangkok 10330",
  "email": "accounts@sample-retail.example",
  "phone": "+66 2 000 0000",
  "notes": "Send statements to the accounts team.",
  "created_at": "2026-10-15T09:12:44+07:00"
}

PATCH /v1/customers/{id}

Update a customer

Changes a customer's name, name_local, address, email, phone or notes, and adds a tax_id and branch_no to a customer that has none. Send only the fields you change; null clears an optional field. tax_id and branch_no cannot change once set: sending a different value is refused with immutable_field (contact SLF if a tax ID was recorded wrongly). A tax_id and branch_no already used by another customer are refused with customer_exists. country and external_id cannot be changed, and other fields in the body are ignored. Documents already recorded keep the details printed on them.

Parameters

Request body

application/json · CustomerUpdate

{
  "email": "ap@sample-retail.example",
  "phone": "+66 2 000 0001"
}

Responses

200 The updated customer. · Customer

{
  "id": "cus_7Hc4Nf2Pq9Xz",
  "external_id": "CUST-00412",
  "name": "Sample Retail Co., Ltd.",
  "name_local": "บริษัท ตัวอย่างค้าปลีก จำกัด",
  "country": "TH",
  "tax_id": "0999000000027",
  "branch_no": "00000",
  "address": "88 Example Road, Pathum Wan, Bangkok 10330",
  "email": "ap@sample-retail.example",
  "phone": "+66 2 000 0001",
  "notes": "Send statements to the accounts team.",
  "created_at": "2026-10-15T09:12:44+07:00"
}

409 Another customer already has this tax_id and branch_no. · Error

{
  "error": {
    "code": "customer_exists",
    "message": "A customer with tax ID 0999000000027, branch 00000 already exists.",
    "param": "/tax_id",
    "details": [],
    "request_id": "req_7d1a4c8e2f6b9a35",
    "existing_id": "cus_7Hc4Nf2Pq9Xz"
  }
}

422 A field is invalid or cannot be changed. · Error

{
  "error": {
    "code": "immutable_field",
    "message": "tax_id cannot be changed once set.",
    "param": "/tax_id",
    "details": [],
    "request_id": "req_0e5a2c8d4f7b1e93",
    "existing_id": null
  }
}

Errors specific to this endpoint

immutable_field, customer_exists. Common errors: see Error codes.

POST /v1/sales-documents

Record a sales document

Records a sales document your system has already issued. Send it exactly as printed: your number, the issue_date, the lines and the totals. The API computes the line amounts and totals and refuses a difference beyond its tolerance (totals_mismatch); within it, the vat_total you printed is recorded (see How the API checks totals). A document whose VAT does not pass SLF's arithmetic check is recorded with the warning vat_arithmetic_review. Disbursement lines (charge_role: disbursement) are recorded as printed and never split; a line priced above its pass_through_cost is refused with disbursement_marked_up, unless your company is not VAT-registered or the document is not in THB. If your company is VAT-registered, a document in which no line carries VAT or says why it does not is refused with vat_category_unexplained. Credit and debit notes also need original_document_ids, reason_code, reason_text, original_value and correct_value (see Corrections); an original that is voided or belongs to another customer is refused with validation_failed. A tax_invoice_receipt is its own receipt and is recorded as paid. A document dated before your start date is refused with validation_failed (out_of_range), and so is a tax_invoice or tax_invoice_receipt dated after today or before the VAT registration date SLF has on record for your company. A tax invoice or cash sale that SLF already entered by hand is refused with recorded_by_slf, and one that repeats the VAT of a receipt with tax_invoice_duplicates_receipt (see Idempotency and duplicates); a foreign-currency one may be refused with fx_basis_unavailable (see Conventions). Tax invoices, cash sales and adjustment notes dated in a month whose VAT return SLF has filed are refused with period_filed (see Filed periods). The example records an invoice with a disbursement line. Its withholding rates (3% on the service lines, none on the disbursement) are only example values, not rules; SLF reviews the rates.

Parameters

Request body

application/json · SalesDocument

{
  "type": "invoice",
  "external_id": "SO-2026-10-0187",
  "number": "INV-2026-0187",
  "issue_date": "2026-10-15",
  "due_date": "2026-11-14",
  "customer_id": "cus_7Hc4Nf2Pq9Xz",
  "currency": "THB",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "remark": "Please pay by bank transfer within 30 days.",
  "reference": "PRJ-2026-031",
  "lines": [
    {
      "name": "Accounting system setup",
      "description": "Chart of accounts, opening balances and user training",
      "quantity": "1",
      "unit_price": "12500.00",
      "vat_category": "standard",
      "wht_rate": "3",
      "item_code": "SVC-SETUP",
      "charge_role": "own_supply"
    },
    {
      "name": "Monthly support",
      "description": "October to December 2026",
      "quantity": "3",
      "unit_price": "2150.75",
      "vat_category": "standard",
      "wht_rate": "3",
      "item_code": "SVC-SUPPORT",
      "charge_role": "own_supply"
    },
    {
      "name": "Government registration fee paid on your behalf",
      "quantity": "1",
      "unit_price": "1500.00",
      "vat_category": "none",
      "wht_rate": "0",
      "charge_role": "disbursement",
      "supplier_invoice_billed_to": "customer",
      "pass_through_cost": "1500.00"
    }
  ],
  "totals": {
    "subtotal": "20452.25",
    "vat_total": "1326.66",
    "total": "21778.91",
    "wht_total": "568.57",
    "net_to_pay": "21210.34"
  }
}

Responses

201 The document was recorded. Check warnings. · SalesDocument

{
  "id": "doc_4Fp9Km2Qx7Ld",
  "type": "invoice",
  "external_id": "SO-2026-10-0187",
  "number": "INV-2026-0187",
  "issue_date": "2026-10-15",
  "due_date": "2026-11-14",
  "valid_until": null,
  "customer_id": "cus_7Hc4Nf2Pq9Xz",
  "bill_to_address": null,
  "currency": "THB",
  "fx_rate": null,
  "fx_date": null,
  "payment_terms": null,
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "remark": "Please pay by bank transfer within 30 days.",
  "reference": "PRJ-2026-031",
  "related_invoice_id": null,
  "replaces_id": null,
  "original_document_ids": null,
  "reason_code": null,
  "reason_text": null,
  "original_value": null,
  "correct_value": null,
  "lines": [
    {
      "name": "Accounting system setup",
      "description": "Chart of accounts, opening balances and user training",
      "quantity": "1",
      "unit_price": "12500.00",
      "vat_category": "standard",
      "wht_rate": "3",
      "item_code": "SVC-SETUP",
      "account_code": null,
      "charge_role": "own_supply",
      "supplier_invoice_billed_to": null,
      "pass_through_cost": null,
      "pre_vat_amount": "12500.00",
      "vat_rate": "7",
      "vat_amount": "875.00",
      "wht_amount": "375.00"
    },
    {
      "name": "Monthly support",
      "description": "October to December 2026",
      "quantity": "3",
      "unit_price": "2150.75",
      "vat_category": "standard",
      "wht_rate": "3",
      "item_code": "SVC-SUPPORT",
      "account_code": null,
      "charge_role": "own_supply",
      "supplier_invoice_billed_to": null,
      "pass_through_cost": null,
      "pre_vat_amount": "6452.25",
      "vat_rate": "7",
      "vat_amount": "451.66",
      "wht_amount": "193.57"
    },
    {
      "name": "Government registration fee paid on your behalf",
      "description": null,
      "quantity": "1",
      "unit_price": "1500.00",
      "vat_category": "none",
      "wht_rate": "0",
      "item_code": null,
      "account_code": null,
      "charge_role": "disbursement",
      "supplier_invoice_billed_to": "customer",
      "pass_through_cost": "1500.00",
      "pre_vat_amount": "1500.00",
      "vat_rate": "0",
      "vat_amount": "0.00",
      "wht_amount": "0.00"
    }
  ],
  "totals": {
    "subtotal": "20452.25",
    "vat_total": "1326.66",
    "total": "21778.91",
    "wht_total": "568.57",
    "net_to_pay": "21210.34"
  },
  "attachments": [],
  "status": "open",
  "paid_amount": "0.00",
  "credited_amount": "0.00",
  "outstanding": "21778.91",
  "voided_at": null,
  "void_reason": null,
  "replaced_by_id": null,
  "warnings": [],
  "created_at": "2026-10-15T14:02:11+07:00"
}

409 A document with this external_id or this number already exists, or SLF already entered this tax invoice or cash sale by hand (recorded_by_slf). · Error

{
  "error": {
    "code": "duplicate_number",
    "message": "An invoice numbered INV-2026-0187 already exists.",
    "param": "/number",
    "details": [],
    "request_id": "req_1e6c3a9d7b2f5c81",
    "existing_id": "doc_4Fp9Km2Qx7Ld"
  }
}

422 The document is invalid, its totals do not match its lines, one of the rules above refuses it, or its month is filed or closed. · Error

{
  "error": {
    "code": "totals_mismatch",
    "message": "Totals do not match the lines.",
    "param": "/totals",
    "details": [
      {
        "param": "/totals/vat_total",
        "code": "mismatch",
        "message": "VAT total differs from the sum of line VAT.",
        "expected": "1326.66",
        "received": "1431.66"
      },
      {
        "param": "/totals/total",
        "code": "mismatch",
        "message": "Total differs from subtotal plus VAT total.",
        "expected": "21778.91",
        "received": "21883.91"
      }
    ],
    "request_id": "req_9a4f7c2e5d8b1a36",
    "existing_id": null
  }
}

Errors specific to this endpoint

duplicate_external_id, duplicate_number, recorded_by_slf, reference_not_found, totals_mismatch, note_difference_mismatch, note_original_not_tax_invoice, note_exceeds_original, disbursement_vat_category, disbursement_marked_up, vat_category_unexplained, tax_invoice_duplicates_receipt, period_filed, period_closed, foreign_currency_tax_invoice_not_allowed, fx_basis_unavailable, fx_rate_required, account_code_unknown. Common errors: see Error codes.

GET /v1/sales-documents

List sales documents

Returns your sales documents, newest first, with optional filters. Documents SLF entered itself are included, such as credit and debit notes; pro-forma documents SLF recorded are not.

Parameters

Responses

200 A page of sales documents. The example holds a foreign-currency invoice, a credit note and the tax invoice it adjusts, whose outstanding the credit note reduced. · list of SalesDocument

{
  "data": [
    {
      "id": "doc_6Xn1Bq5Ty3Gv",
      "type": "invoice",
      "external_id": "SO-2026-10-0192",
      "number": "INV-2026-0192",
      "issue_date": "2026-10-27",
      "due_date": "2026-11-26",
      "valid_until": null,
      "customer_id": "cus_3Wd8Lm5Tb2Kr",
      "bill_to_address": null,
      "currency": "USD",
      "fx_rate": "32.4512",
      "fx_date": "2026-10-27",
      "payment_terms": "tt",
      "bank_account_id": "bnk_9Ze3Lp6Qr2Dn",
      "remark": null,
      "reference": null,
      "related_invoice_id": null,
      "replaces_id": null,
      "original_document_ids": null,
      "reason_code": null,
      "reason_text": null,
      "original_value": null,
      "correct_value": null,
      "lines": [
        {
          "name": "Teak serving tray, large",
          "description": null,
          "quantity": "120",
          "unit_price": "18.75",
          "vat_category": "zero",
          "wht_rate": "0",
          "item_code": "TRAY-L",
          "account_code": null,
          "charge_role": null,
          "supplier_invoice_billed_to": null,
          "pass_through_cost": null,
          "pre_vat_amount": "2250.00",
          "vat_rate": "0",
          "vat_amount": "0.00",
          "wht_amount": "0.00"
        },
        {
          "name": "Teak serving tray, small",
          "description": null,
          "quantity": "200",
          "unit_price": "9.40",
          "vat_category": "zero",
          "wht_rate": "0",
          "item_code": "TRAY-S",
          "account_code": null,
          "charge_role": null,
          "supplier_invoice_billed_to": null,
          "pass_through_cost": null,
          "pre_vat_amount": "1880.00",
          "vat_rate": "0",
          "vat_amount": "0.00",
          "wht_amount": "0.00"
        }
      ],
      "totals": {
        "subtotal": "4130.00",
        "vat_total": "0.00",
        "total": "4130.00",
        "wht_total": null,
        "net_to_pay": null
      },
      "attachments": [],
      "status": "open",
      "paid_amount": "0.00",
      "credited_amount": "0.00",
      "outstanding": "4130.00",
      "voided_at": null,
      "void_reason": null,
      "replaced_by_id": null,
      "warnings": [
        {
          "code": "zero_rated_review",
          "message": "Line 1 uses the 0% rate. SLF will check that the conditions for it are met.",
          "param": "/lines/0/vat_category"
        },
        {
          "code": "zero_rated_review",
          "message": "Line 2 uses the 0% rate. SLF will check that the conditions for it are met.",
          "param": "/lines/1/vat_category"
        }
      ],
      "created_at": "2026-10-27T15:20:48+07:00"
    },
    {
      "id": "doc_2Lk7Pw4Mc8Jq",
      "type": "credit_note",
      "external_id": "SO-CN-2026-10-0031",
      "number": "CN-2026-0031",
      "issue_date": "2026-10-22",
      "due_date": null,
      "valid_until": null,
      "customer_id": "cus_7Hc4Nf2Pq9Xz",
      "bill_to_address": null,
      "currency": "THB",
      "fx_rate": null,
      "fx_date": null,
      "payment_terms": null,
      "bank_account_id": null,
      "remark": null,
      "reference": null,
      "related_invoice_id": null,
      "replaces_id": null,
      "original_document_ids": [
        "doc_9Rt3Vb6Nz1Hs"
      ],
      "reason_code": "goods_returned",
      "reason_text": "2 chairs returned: gas lift defective",
      "original_value": "29168.00",
      "correct_value": "24268.00",
      "lines": [
        {
          "name": "Office chair, model A (returned)",
          "description": null,
          "quantity": "2",
          "unit_price": "2450.00",
          "vat_category": "standard",
          "wht_rate": "0",
          "item_code": "CH-A",
          "account_code": null,
          "charge_role": null,
          "supplier_invoice_billed_to": null,
          "pass_through_cost": null,
          "pre_vat_amount": "4900.00",
          "vat_rate": "7",
          "vat_amount": "343.00",
          "wht_amount": "0.00"
        }
      ],
      "totals": {
        "subtotal": "4900.00",
        "vat_total": "343.00",
        "total": "5243.00",
        "wht_total": null,
        "net_to_pay": null
      },
      "attachments": [],
      "status": "open",
      "paid_amount": "0.00",
      "credited_amount": "0.00",
      "outstanding": "0.00",
      "voided_at": null,
      "void_reason": null,
      "replaced_by_id": null,
      "warnings": [],
      "created_at": "2026-10-22T10:31:09+07:00"
    },
    {
      "id": "doc_9Rt3Vb6Nz1Hs",
      "type": "tax_invoice",
      "external_id": "SO-2026-10-0412",
      "number": "TIV-2026-0412",
      "issue_date": "2026-10-08",
      "due_date": "2026-11-07",
      "valid_until": null,
      "customer_id": "cus_7Hc4Nf2Pq9Xz",
      "bill_to_address": null,
      "currency": "THB",
      "fx_rate": null,
      "fx_date": null,
      "payment_terms": null,
      "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
      "remark": null,
      "reference": null,
      "related_invoice_id": null,
      "replaces_id": null,
      "original_document_ids": null,
      "reason_code": null,
      "reason_text": null,
      "original_value": null,
      "correct_value": null,
      "lines": [
        {
          "name": "Office chair, model A",
          "description": null,
          "quantity": "10",
          "unit_price": "2450.00",
          "vat_category": "standard",
          "wht_rate": "0",
          "item_code": "CH-A",
          "account_code": null,
          "charge_role": null,
          "supplier_invoice_billed_to": null,
          "pass_through_cost": null,
          "pre_vat_amount": "24500.00",
          "vat_rate": "7",
          "vat_amount": "1715.00",
          "wht_amount": "0.00"
        },
        {
          "name": "Desk lamp, LED",
          "description": null,
          "quantity": "12",
          "unit_price": "389.00",
          "vat_category": "standard",
          "wht_rate": "0",
          "item_code": "LAMP-LED",
          "account_code": null,
          "charge_role": null,
          "supplier_invoice_billed_to": null,
          "pass_through_cost": null,
          "pre_vat_amount": "4668.00",
          "vat_rate": "7",
          "vat_amount": "326.76",
          "wht_amount": "0.00"
        }
      ],
      "totals": {
        "subtotal": "29168.00",
        "vat_total": "2041.76",
        "total": "31209.76",
        "wht_total": null,
        "net_to_pay": null
      },
      "attachments": [
        {
          "id": "att_2Bh5Rx8Fk3Wq",
          "object_type": "sales_document",
          "object_id": "doc_9Rt3Vb6Nz1Hs",
          "kind": "document_copy",
          "file_name": "TIV-2026-0412.pdf",
          "content_type": "application/pdf",
          "size": 184233,
          "sha256": "9f2b5c1e7a4d8f0c3b6e9a2d5c8f1b4e7a0d3c6f9b2e5a8d1c4f7b0e3a6d9c2f",
          "created_at": "2026-10-08T11:05:37+07:00"
        }
      ],
      "status": "open",
      "paid_amount": "0.00",
      "credited_amount": "5243.00",
      "outstanding": "25966.76",
      "voided_at": null,
      "void_reason": null,
      "replaced_by_id": null,
      "warnings": [],
      "created_at": "2026-10-08T11:04:52+07:00"
    }
  ],
  "next_cursor": null
}

GET /v1/sales-documents/{id}

Get a sales document

Returns one sales document, with its lines, totals, attachments, payment status and warnings. A pro-forma document SLF recorded answers 404 not_found.

Parameters

Responses

200 The sales document. · SalesDocument

{
  "id": "doc_9Rt3Vb6Nz1Hs",
  "type": "tax_invoice",
  "external_id": "SO-2026-10-0412",
  "number": "TIV-2026-0412",
  "issue_date": "2026-10-08",
  "due_date": "2026-11-07",
  "valid_until": null,
  "customer_id": "cus_7Hc4Nf2Pq9Xz",
  "bill_to_address": null,
  "currency": "THB",
  "fx_rate": null,
  "fx_date": null,
  "payment_terms": null,
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "remark": null,
  "reference": null,
  "related_invoice_id": null,
  "replaces_id": null,
  "original_document_ids": null,
  "reason_code": null,
  "reason_text": null,
  "original_value": null,
  "correct_value": null,
  "lines": [
    {
      "name": "Office chair, model A",
      "description": null,
      "quantity": "10",
      "unit_price": "2450.00",
      "vat_category": "standard",
      "wht_rate": "0",
      "item_code": "CH-A",
      "account_code": null,
      "charge_role": null,
      "supplier_invoice_billed_to": null,
      "pass_through_cost": null,
      "pre_vat_amount": "24500.00",
      "vat_rate": "7",
      "vat_amount": "1715.00",
      "wht_amount": "0.00"
    },
    {
      "name": "Desk lamp, LED",
      "description": null,
      "quantity": "12",
      "unit_price": "389.00",
      "vat_category": "standard",
      "wht_rate": "0",
      "item_code": "LAMP-LED",
      "account_code": null,
      "charge_role": null,
      "supplier_invoice_billed_to": null,
      "pass_through_cost": null,
      "pre_vat_amount": "4668.00",
      "vat_rate": "7",
      "vat_amount": "326.76",
      "wht_amount": "0.00"
    }
  ],
  "totals": {
    "subtotal": "29168.00",
    "vat_total": "2041.76",
    "total": "31209.76",
    "wht_total": null,
    "net_to_pay": null
  },
  "attachments": [
    {
      "id": "att_2Bh5Rx8Fk3Wq",
      "object_type": "sales_document",
      "object_id": "doc_9Rt3Vb6Nz1Hs",
      "kind": "document_copy",
      "file_name": "TIV-2026-0412.pdf",
      "content_type": "application/pdf",
      "size": 184233,
      "sha256": "9f2b5c1e7a4d8f0c3b6e9a2d5c8f1b4e7a0d3c6f9b2e5a8d1c4f7b0e3a6d9c2f",
      "created_at": "2026-10-08T11:05:37+07:00"
    }
  ],
  "status": "open",
  "paid_amount": "0.00",
  "credited_amount": "5243.00",
  "outstanding": "25966.76",
  "voided_at": null,
  "void_reason": null,
  "replaced_by_id": null,
  "warnings": [],
  "created_at": "2026-10-08T11:04:52+07:00"
}

POST /v1/sales-documents/{id}/void

Void a sales document

Voids a sales document. For a quotation or invoice, this records your cancellation. To cancel and reissue a tax_invoice or tax_invoice_receipt, first record the replacement (new number, issue_date equal to the original's, replaces_id set to the original), then void the original with replacement_id; see Corrections for the Revenue Department procedure. Credit and debit notes cannot be voided through the API (note_cannot_be_voided). A voided document keeps its number and is returned with status: void. Voiding a tax invoice, cash sale or note dated in a filed month is refused with period_filed, and one dated in a closed period with period_closed. A document cannot be voided while receipts recorded against it are not voided (void them first), while a credit or debit note is recorded against it, or once SLF has posted it to your books (void_not_allowed).

Parameters

Request body

application/json · SalesDocumentVoidRequest

{
  "reason": "Buyer's address was wrong. Replaced by TIV-2026-0415.",
  "replacement_id": "doc_8Jd2Sv6Wm4Pa"
}

Responses

200 The voided document. · SalesDocument

{
  "id": "doc_1Gh6Tc9Rw2Ne",
  "type": "tax_invoice",
  "external_id": "SO-2026-10-0398",
  "number": "TIV-2026-0398",
  "issue_date": "2026-10-05",
  "due_date": null,
  "valid_until": null,
  "customer_id": "cus_7Hc4Nf2Pq9Xz",
  "bill_to_address": "8 Example Road, Pathum Wan, Bangkok 10330",
  "currency": "THB",
  "fx_rate": null,
  "fx_date": null,
  "payment_terms": null,
  "bank_account_id": null,
  "remark": null,
  "reference": null,
  "related_invoice_id": null,
  "replaces_id": null,
  "original_document_ids": null,
  "reason_code": null,
  "reason_text": null,
  "original_value": null,
  "correct_value": null,
  "lines": [
    {
      "name": "Bookkeeping software licence, 12 months",
      "description": null,
      "quantity": "1",
      "unit_price": "18000.00",
      "vat_category": "standard",
      "wht_rate": "0",
      "item_code": "LIC-12M",
      "account_code": null,
      "charge_role": null,
      "supplier_invoice_billed_to": null,
      "pass_through_cost": null,
      "pre_vat_amount": "18000.00",
      "vat_rate": "7",
      "vat_amount": "1260.00",
      "wht_amount": "0.00"
    }
  ],
  "totals": {
    "subtotal": "18000.00",
    "vat_total": "1260.00",
    "total": "19260.00",
    "wht_total": null,
    "net_to_pay": null
  },
  "attachments": [],
  "status": "void",
  "paid_amount": "0.00",
  "credited_amount": "0.00",
  "outstanding": "0.00",
  "voided_at": "2026-10-29T13:47:20+07:00",
  "void_reason": "Buyer's address was wrong. Replaced by TIV-2026-0415.",
  "replaced_by_id": "doc_8Jd2Sv6Wm4Pa",
  "warnings": [],
  "created_at": "2026-10-05T10:15:02+07:00"
}

409 The document is already voided (already_voided), or it cannot be voided now (void_not_allowed). · Error

{
  "error": {
    "code": "void_not_allowed",
    "message": "Receipt RE-2026-0233 is recorded against this invoice. Void the receipt first.",
    "param": null,
    "details": [],
    "request_id": "req_8d4f2b7e1a6c9d53",
    "existing_id": null
  }
}

422 The document cannot be voided through the API, or its month is filed or closed. · Error

{
  "error": {
    "code": "period_filed",
    "message": "This tax invoice is dated in 2026-09, whose VAT return SLF has already filed. Contact SLF.",
    "param": null,
    "details": [],
    "request_id": "req_3e8b1d6a9c2f5e47",
    "existing_id": null
  }
}

Errors specific to this endpoint

already_voided, void_not_allowed, note_cannot_be_voided, reference_not_found, period_filed, period_closed. Common errors: see Error codes.

POST /v1/receipts

Record a receipt

Records a payment received against an invoice, tax_invoice or debit_note. amount_received is the money that arrived; wht_amount is the tax the customer withheld. Their sum, gross_amount, reduces the document's outstanding and may not exceed it (receipt_exceeds_outstanding). wht_amount may not exceed the withholding still expected from the document lines' wht_rate (wht_exceeds_expected); if it implies a different rate, the receipt is recorded with the warning wht_rate_review. A quotation, a tax_invoice_receipt (it is its own receipt), a credit note or a voided document cannot be receipted (receipt_not_allowed). The receipt takes the document's currency and exchange rate. A receipt that books VAT is checked against the month of its payment_date (period_filed), and any receipt dated in a closed period is refused (period_closed). A payment_date after today or before your start date is refused with validation_failed (out_of_range). Your receipt number must be unique among your receipts that are not voided (duplicate_number). A receipt for less than the document still owes is recorded with the warning short_payment, and your remark is stored unchanged. If SLF had entered by hand the VAT of the document being paid (an entry with its number and total), a receipt that books VAT depends on that entry's month. In a month whose VAT return SLF has filed, the receipt is recorded with the warning recorded_by_slf_filed, whether or not the entry is posted. In a month not yet filed, the receipt takes the entry's place, unless SLF has posted the entry to your books: then the receipt is refused with 409 recorded_by_slf_posted. A receipt that books VAT for a customer who has a tax_invoice that is not voided, of the same amount, without related_invoice_id, dated in the month of the receipt's payment_date, is recorded with the warning possible_double_vat.

Parameters

Request body

application/json · Receipt

{
  "external_id": "RCV-2026-10-0233",
  "number": "RE-2026-0233",
  "document_id": "doc_4Fp9Km2Qx7Ld",
  "payment_date": "2026-10-30",
  "amount_received": "21210.34",
  "wht_amount": "568.57",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "remark": "Customer withheld 3% on the service lines; 50 ทวิ certificate received."
}

Responses

201 The receipt was recorded. Check warnings. · Receipt

{
  "id": "rcp_3Np8Gz5Kd1Vt",
  "external_id": "RCV-2026-10-0233",
  "number": "RE-2026-0233",
  "document_id": "doc_4Fp9Km2Qx7Ld",
  "payment_date": "2026-10-30",
  "amount_received": "21210.34",
  "wht_amount": "568.57",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "remark": "Customer withheld 3% on the service lines; 50 ทวิ certificate received.",
  "gross_amount": "21778.91",
  "vat_amount": "1326.66",
  "currency": "THB",
  "fx_rate": null,
  "attachments": [],
  "warnings": [],
  "voided_at": null,
  "void_reason": null,
  "created_at": "2026-10-30T17:08:26+07:00"
}

409 A receipt with this external_id or number already exists, or SLF has posted its own hand entry for this document's VAT in a month it has not filed (recorded_by_slf_posted). · Error

{
  "error": {
    "code": "duplicate_external_id",
    "message": "A receipt with external_id RCV-2026-10-0233 already exists.",
    "param": "/external_id",
    "details": [],
    "request_id": "req_7a3e9c1d5b8f2a64",
    "existing_id": "rcp_3Np8Gz5Kd1Vt"
  }
}

422 The receipt is invalid or not allowed for this document. · Error

{
  "error": {
    "code": "receipt_exceeds_outstanding",
    "message": "amount_received plus wht_amount (21778.91) is more than the outstanding 10000.00.",
    "param": "/amount_received",
    "details": [],
    "request_id": "req_2d7a5c9f3e1b8d42",
    "existing_id": null
  }
}

Errors specific to this endpoint

duplicate_external_id, duplicate_number, recorded_by_slf_posted, reference_not_found, receipt_not_allowed, receipt_exceeds_outstanding, wht_exceeds_expected, period_filed, period_closed. Common errors: see Error codes.

GET /v1/receipts

List receipts

Returns your receipts, newest first.

Parameters

Responses

200 A page of receipts. · list of Receipt

{
  "data": [
    {
      "id": "rcp_3Np8Gz5Kd1Vt",
      "external_id": "RCV-2026-10-0233",
      "number": "RE-2026-0233",
      "document_id": "doc_4Fp9Km2Qx7Ld",
      "payment_date": "2026-10-30",
      "amount_received": "21210.34",
      "wht_amount": "568.57",
      "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
      "remark": "Customer withheld 3% on the service lines; 50 ทวิ certificate received.",
      "gross_amount": "21778.91",
      "vat_amount": "1326.66",
      "currency": "THB",
      "fx_rate": null,
      "attachments": [],
      "warnings": [],
      "voided_at": null,
      "void_reason": null,
      "created_at": "2026-10-30T17:08:26+07:00"
    }
  ],
  "next_cursor": null
}

GET /v1/receipts/{id}

Get a receipt

Returns one receipt.

Parameters

Responses

200 The receipt. · Receipt

{
  "id": "rcp_3Np8Gz5Kd1Vt",
  "external_id": "RCV-2026-10-0233",
  "number": "RE-2026-0233",
  "document_id": "doc_4Fp9Km2Qx7Ld",
  "payment_date": "2026-10-30",
  "amount_received": "21210.34",
  "wht_amount": "568.57",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "remark": "Customer withheld 3% on the service lines; 50 ทวิ certificate received.",
  "gross_amount": "21778.91",
  "vat_amount": "1326.66",
  "currency": "THB",
  "fx_rate": null,
  "attachments": [],
  "warnings": [],
  "voided_at": null,
  "void_reason": null,
  "created_at": "2026-10-30T17:08:26+07:00"
}

POST /v1/receipts/{id}/void

Void a receipt

Voids a receipt recorded by mistake. The document's outstanding goes back up by the receipt's gross_amount. A receipt that booked VAT cannot be voided once its month is filed (period_filed), and no receipt can be voided once its payment_date falls in a closed period (period_closed). It is also refused with void_not_allowed once SLF has posted it to your books, while a credit or debit note is recorded against it or a credit note depends on it, and while a tax_invoice with related_invoice_id stands on its invoice. If the receipt took the place of a VAT entry SLF had made by hand, voiding it restores that entry.

Parameters

Request body

application/json · VoidRequest

{
  "reason": "Recorded against the wrong invoice."
}

Responses

200 The voided receipt. · Receipt

{
  "id": "rcp_3Np8Gz5Kd1Vt",
  "external_id": "RCV-2026-10-0233",
  "number": "RE-2026-0233",
  "document_id": "doc_4Fp9Km2Qx7Ld",
  "payment_date": "2026-10-30",
  "amount_received": "21210.34",
  "wht_amount": "568.57",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "remark": "Customer withheld 3% on the service lines; 50 ทวิ certificate received.",
  "gross_amount": "21778.91",
  "vat_amount": "1326.66",
  "currency": "THB",
  "fx_rate": null,
  "attachments": [],
  "warnings": [],
  "voided_at": "2026-10-31T09:03:12+07:00",
  "void_reason": "Recorded against the wrong invoice.",
  "created_at": "2026-10-30T17:08:26+07:00"
}

409 The receipt is already voided (already_voided), or it cannot be voided now (void_not_allowed). · Error

{
  "error": {
    "code": "already_voided",
    "message": "This record is already voided.",
    "param": null,
    "details": [],
    "request_id": "req_5c9a1e7d3b6f2a48",
    "existing_id": null
  }
}

422 The receipt is dated in a filed month or a closed period. · Error

{
  "error": {
    "code": "period_filed",
    "message": "This receipt booked VAT in a month whose VAT return SLF has already filed. Contact SLF.",
    "param": null,
    "details": [],
    "request_id": "req_9b2e6c4a8d1f3e75",
    "existing_id": null
  }
}

Errors specific to this endpoint

already_voided, void_not_allowed, period_filed, period_closed. Common errors: see Error codes.

POST /v1/bills

Record a supplier bill

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Records a document you received from a supplier. Amounts are typed from the printed document and are not recomputed; the API only checks that total equals subtotal plus vat_amount (totals_mismatch). Lines are optional and help SLF classify the cost; their amounts are not added up against the header. A second bill with the same supplier tax_id (or, for a supplier without one, the same supplier name) and bill_number is refused with 409 duplicate_bill. If the bill is a cost you paid on a customer's behalf and is addressed to that customer, set on_behalf_of_customer_id.

Parameters

Request body

application/json · Bill

{
  "external_id": "AP-2026-10-0058",
  "document_type": "tax_invoice",
  "supplier": {
    "name": "Demo Services Co., Ltd.",
    "tax_id": "0999000000035",
    "branch_no": "00000",
    "country": "TH"
  },
  "bill_number": "DS-2610-0058",
  "bill_date": "2026-10-25",
  "due_date": "2026-11-24",
  "currency": "THB",
  "subtotal": "15000.00",
  "vat_amount": "1050.00",
  "total": "16050.00",
  "lines": [
    {
      "description": "IT support, October 2026",
      "quantity": "1",
      "unit_price": "15000.00",
      "amount": "15000.00",
      "item_code": "DS-ITS-01"
    }
  ],
  "remark": "Monthly IT support contract",
  "reference": null
}

Responses

201 The bill was recorded. · Bill

{
  "id": "bil_5Tg9Hw2Lr6Mx",
  "external_id": "AP-2026-10-0058",
  "document_type": "tax_invoice",
  "supplier": {
    "name": "Demo Services Co., Ltd.",
    "tax_id": "0999000000035",
    "branch_no": "00000",
    "country": "TH"
  },
  "bill_number": "DS-2610-0058",
  "bill_date": "2026-10-25",
  "due_date": "2026-11-24",
  "currency": "THB",
  "fx_rate": null,
  "fx_date": null,
  "subtotal": "15000.00",
  "vat_amount": "1050.00",
  "total": "16050.00",
  "lines": [
    {
      "description": "IT support, October 2026",
      "quantity": "1",
      "unit_price": "15000.00",
      "amount": "15000.00",
      "item_code": "DS-ITS-01",
      "account_code": null
    }
  ],
  "on_behalf_of_customer_id": null,
  "remark": "Monthly IT support contract",
  "reference": null,
  "status": "open",
  "paid_amount": "0.00",
  "outstanding": "16050.00",
  "notes": [],
  "attachments": [],
  "voided_at": null,
  "void_reason": null,
  "created_at": "2026-10-26T09:41:15+07:00"
}

409 A bill with this external_id, or this supplier tax_id and bill_number, already exists. · Error

{
  "error": {
    "code": "duplicate_bill",
    "message": "A bill DS-2610-0058 from supplier 0999000000035 already exists.",
    "param": "/bill_number",
    "details": [],
    "request_id": "req_8c2e6a4f1d9b3c75",
    "existing_id": "bil_5Tg9Hw2Lr6Mx"
  }
}

422 The bill is invalid. · Error

{
  "error": {
    "code": "validation_failed",
    "message": "2 fields are invalid.",
    "param": null,
    "details": [
      {
        "param": "/tax_id",
        "code": "invalid_tax_id",
        "message": "The check digit does not match.",
        "expected": null,
        "received": null
      },
      {
        "param": "/email",
        "code": "invalid_format",
        "message": "Not an email address.",
        "expected": null,
        "received": null
      }
    ],
    "request_id": "req_3c9e1f7a2b5d8c04",
    "existing_id": null
  }
}

Errors specific to this endpoint

duplicate_external_id, duplicate_bill, reference_not_found, totals_mismatch, fx_rate_required, account_code_unknown. Common errors: see Error codes.

GET /v1/bills

List supplier bills

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Returns your supplier bills, newest first.

Parameters

Responses

200 A page of bills. · list of Bill

{
  "data": [
    {
      "id": "bil_5Tg9Hw2Lr6Mx",
      "external_id": "AP-2026-10-0058",
      "document_type": "tax_invoice",
      "supplier": {
        "name": "Demo Services Co., Ltd.",
        "tax_id": "0999000000035",
        "branch_no": "00000",
        "country": "TH"
      },
      "bill_number": "DS-2610-0058",
      "bill_date": "2026-10-25",
      "due_date": "2026-11-24",
      "currency": "THB",
      "fx_rate": null,
      "fx_date": null,
      "subtotal": "15000.00",
      "vat_amount": "1050.00",
      "total": "16050.00",
      "lines": [
        {
          "description": "IT support, October 2026",
          "quantity": "1",
          "unit_price": "15000.00",
          "amount": "15000.00",
          "item_code": "DS-ITS-01",
          "account_code": null
        }
      ],
      "on_behalf_of_customer_id": null,
      "remark": "Monthly IT support contract",
      "reference": null,
      "status": "open",
      "paid_amount": "0.00",
      "outstanding": "16050.00",
      "notes": [],
      "attachments": [],
      "voided_at": null,
      "void_reason": null,
      "created_at": "2026-10-26T09:41:15+07:00"
    }
  ],
  "next_cursor": null
}

GET /v1/bills/{id}

Get a supplier bill

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Returns one bill, with its payment status and any supplier notes recorded against it.

Parameters

Responses

200 The bill. · Bill

{
  "id": "bil_5Tg9Hw2Lr6Mx",
  "external_id": "AP-2026-10-0058",
  "document_type": "tax_invoice",
  "supplier": {
    "name": "Demo Services Co., Ltd.",
    "tax_id": "0999000000035",
    "branch_no": "00000",
    "country": "TH"
  },
  "bill_number": "DS-2610-0058",
  "bill_date": "2026-10-25",
  "due_date": "2026-11-24",
  "currency": "THB",
  "fx_rate": null,
  "fx_date": null,
  "subtotal": "15000.00",
  "vat_amount": "1050.00",
  "total": "16050.00",
  "lines": [
    {
      "description": "IT support, October 2026",
      "quantity": "1",
      "unit_price": "15000.00",
      "amount": "15000.00",
      "item_code": "DS-ITS-01",
      "account_code": null
    }
  ],
  "on_behalf_of_customer_id": null,
  "remark": "Monthly IT support contract",
  "reference": null,
  "status": "open",
  "paid_amount": "0.00",
  "outstanding": "16050.00",
  "notes": [],
  "attachments": [],
  "voided_at": null,
  "void_reason": null,
  "created_at": "2026-10-26T09:41:15+07:00"
}

POST /v1/bills/{id}/void

Void a supplier bill

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Voids a bill recorded by mistake. It stays visible with status: void. A bill cannot be voided while payments allocated to it are not reversed (reverse them first), or while a supplier note on it has been posted by SLF to your books (void_not_allowed).

Parameters

Request body

application/json · VoidRequest

{
  "reason": "The supplier withdrew this bill."
}

Responses

200 The voided bill. · Bill

{
  "id": "bil_8Kd3Wq6Ln1Rz",
  "external_id": "AP-2026-10-0057",
  "document_type": "tax_invoice",
  "supplier": {
    "name": "Demo Services Co., Ltd.",
    "tax_id": "0999000000035",
    "branch_no": "00000",
    "country": "TH"
  },
  "bill_number": "DS-2610-0057",
  "bill_date": "2026-10-25",
  "due_date": "2026-11-24",
  "currency": "THB",
  "fx_rate": null,
  "fx_date": null,
  "subtotal": "15000.00",
  "vat_amount": "1050.00",
  "total": "16050.00",
  "lines": [
    {
      "description": "IT support, October 2026",
      "quantity": "1",
      "unit_price": "15000.00",
      "amount": "15000.00",
      "item_code": "DS-ITS-01",
      "account_code": null
    }
  ],
  "on_behalf_of_customer_id": null,
  "remark": "Monthly IT support contract",
  "reference": null,
  "status": "void",
  "paid_amount": "0.00",
  "outstanding": "0.00",
  "notes": [],
  "attachments": [],
  "voided_at": "2026-10-27T08:30:00+07:00",
  "void_reason": "The supplier withdrew this bill.",
  "created_at": "2026-10-26T09:41:15+07:00"
}

409 The bill is already voided (already_voided), or it cannot be voided now (void_not_allowed). · Error

{
  "error": {
    "code": "already_voided",
    "message": "This record is already voided.",
    "param": null,
    "details": [],
    "request_id": "req_5c9a1e7d3b6f2a48",
    "existing_id": null
  }
}

Errors specific to this endpoint

already_voided, void_not_allowed. Common errors: see Error codes.

POST /v1/bills/{id}/notes

Record a supplier credit or debit note

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Records a credit or debit note your supplier issued against a bill. amount is the change before VAT and vat_amount the VAT on it, both as printed; reason is the supplier's reason, as free text. The note changes the bill's outstanding. A credit note may not be more than the bill's total less the supplier credit notes already recorded against it (validation_failed, out_of_range), and no note is accepted on a voided bill.

Parameters

Request body

application/json · BillNote

{
  "external_id": "AP-CN-2026-11-0007",
  "type": "credit_note",
  "number": "DS-CN-0007",
  "date": "2026-11-02",
  "amount": "1000.00",
  "vat_amount": "70.00",
  "reason": "Two support visits were not provided"
}

Responses

201 The note was recorded. · BillNote

{
  "id": "bnt_1Qz6Ck3Pv8Ys",
  "bill_id": "bil_2Cw8Np4Vs7Kf",
  "external_id": "AP-CN-2026-11-0007",
  "type": "credit_note",
  "number": "DS-CN-0007",
  "date": "2026-11-02",
  "amount": "1000.00",
  "vat_amount": "70.00",
  "reason": "Two support visits were not provided",
  "created_at": "2026-11-02T14:22:40+07:00"
}

409 A supplier note with this external_id already exists. · Error

{
  "error": {
    "code": "duplicate_external_id",
    "message": "A supplier note with external_id AP-CN-2026-11-0007 already exists.",
    "param": "/external_id",
    "details": [],
    "request_id": "req_6a2d9f4c1e8b3a70",
    "existing_id": "bnt_1Qz6Ck3Pv8Ys"
  }
}

422 The note is invalid. · Error

{
  "error": {
    "code": "validation_failed",
    "message": "2 fields are invalid.",
    "param": null,
    "details": [
      {
        "param": "/tax_id",
        "code": "invalid_tax_id",
        "message": "The check digit does not match.",
        "expected": null,
        "received": null
      },
      {
        "param": "/email",
        "code": "invalid_format",
        "message": "Not an email address.",
        "expected": null,
        "received": null
      }
    ],
    "request_id": "req_3c9e1f7a2b5d8c04",
    "existing_id": null
  }
}

Errors specific to this endpoint

duplicate_external_id. Common errors: see Error codes.

POST /v1/payments

Record a supplier payment

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Records a payment you made. Each allocation gives the cash paid towards one bill and the tax you withheld from it, in the bill's currency; together they reduce the bill's outstanding, and an allocation larger than the outstanding is refused with validation_failed (out_of_range). When you withheld tax, list it in withholding, one entry per payee and income type, as on your 50 ทวิ certificate. Withholding entries are in THB, so a payment with withholding may be allocated only to bills in THB (validation_failed, invalid_value). The withheld amounts in allocations and in withholding must add up to the same total (withholding_mismatch), and each entry's wht_amount must equal round2(gross_amount × rate / 100) (totals_mismatch). return_form is set from payee_type, and SLF confirms it on review. A payment with withholding dated in a month whose withholding return of that return_form SLF has filed is refused with period_filed; any payment dated in a closed period with period_closed. Rates are what you actually withheld; the API does not check them against income types, and SLF reviews them. The example withholds 3% on a service fee; the number is only an example, not a rule.

Parameters

Request body

application/json · Payment

{
  "external_id": "AP-PAY-2026-10-0031",
  "pay_date": "2026-10-31",
  "method": "transfer",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "reference": "TRF-20261031-0007",
  "allocations": [
    {
      "bill_id": "bil_5Tg9Hw2Lr6Mx",
      "amount": "15600.00",
      "wht_amount": "450.00"
    }
  ],
  "withholding": [
    {
      "payee_name": "Demo Services Co., Ltd.",
      "payee_tax_id": "0999000000035",
      "payee_branch_no": "00000",
      "payee_address": "1 Example Road, Khlong Toei, Bangkok 10110",
      "payee_type": "company",
      "income_type": "service",
      "income_description": null,
      "gross_amount": "15000.00",
      "rate": "3",
      "wht_amount": "450.00",
      "certificate_number": "WHT-2026-0101"
    }
  ]
}

Responses

201 The payment was recorded. · Payment

{
  "id": "pay_7Mv4Ys1Jn9Bc",
  "external_id": "AP-PAY-2026-10-0031",
  "pay_date": "2026-10-31",
  "method": "transfer",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "reference": "TRF-20261031-0007",
  "allocations": [
    {
      "bill_id": "bil_5Tg9Hw2Lr6Mx",
      "amount": "15600.00",
      "wht_amount": "450.00"
    }
  ],
  "withholding": [
    {
      "payee_name": "Demo Services Co., Ltd.",
      "payee_tax_id": "0999000000035",
      "payee_branch_no": "00000",
      "payee_address": "1 Example Road, Khlong Toei, Bangkok 10110",
      "payee_type": "company",
      "income_type": "service",
      "income_description": null,
      "gross_amount": "15000.00",
      "rate": "3",
      "wht_amount": "450.00",
      "certificate_number": "WHT-2026-0101",
      "return_form": "pnd53"
    }
  ],
  "attachments": [],
  "state": "recorded",
  "reversed_at": null,
  "reverse_reason": null,
  "created_at": "2026-10-31T16:55:02+07:00"
}

409 A payment with this external_id already exists. · Error

{
  "error": {
    "code": "duplicate_external_id",
    "message": "A payment with external_id AP-PAY-2026-10-0031 already exists.",
    "param": "/external_id",
    "details": [],
    "request_id": "req_1c7e4a9d2f6b8e53",
    "existing_id": "pay_7Mv4Ys1Jn9Bc"
  }
}

422 The payment is invalid, its withholding does not add up, or its month is filed or closed. · Error

{
  "error": {
    "code": "withholding_mismatch",
    "message": "allocations withhold 450.00 in total but withholding lists 405.00.",
    "param": "/withholding",
    "details": [
      {
        "param": "/withholding",
        "code": "mismatch",
        "message": "Sum of withholding[].wht_amount.",
        "expected": "450.00",
        "received": "405.00"
      }
    ],
    "request_id": "req_4b1d8f3a6c2e9d17",
    "existing_id": null
  }
}

Errors specific to this endpoint

duplicate_external_id, reference_not_found, withholding_mismatch, totals_mismatch, period_filed, period_closed. Common errors: see Error codes.

GET /v1/payments

List supplier payments

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Returns your supplier payments, newest first.

Parameters

Responses

200 A page of payments. · list of Payment

{
  "data": [
    {
      "id": "pay_7Mv4Ys1Jn9Bc",
      "external_id": "AP-PAY-2026-10-0031",
      "pay_date": "2026-10-31",
      "method": "transfer",
      "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
      "reference": "TRF-20261031-0007",
      "allocations": [
        {
          "bill_id": "bil_5Tg9Hw2Lr6Mx",
          "amount": "15600.00",
          "wht_amount": "450.00"
        }
      ],
      "withholding": [
        {
          "payee_name": "Demo Services Co., Ltd.",
          "payee_tax_id": "0999000000035",
          "payee_branch_no": "00000",
          "payee_address": "1 Example Road, Khlong Toei, Bangkok 10110",
          "payee_type": "company",
          "income_type": "service",
          "income_description": null,
          "gross_amount": "15000.00",
          "rate": "3",
          "wht_amount": "450.00",
          "certificate_number": "WHT-2026-0101",
          "return_form": "pnd53"
        }
      ],
      "attachments": [],
      "state": "recorded",
      "reversed_at": null,
      "reverse_reason": null,
      "created_at": "2026-10-31T16:55:02+07:00"
    }
  ],
  "next_cursor": null
}

GET /v1/payments/{id}

Get a supplier payment

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Returns one payment, with its allocations and withholding.

Parameters

Responses

200 The payment. · Payment

{
  "id": "pay_7Mv4Ys1Jn9Bc",
  "external_id": "AP-PAY-2026-10-0031",
  "pay_date": "2026-10-31",
  "method": "transfer",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "reference": "TRF-20261031-0007",
  "allocations": [
    {
      "bill_id": "bil_5Tg9Hw2Lr6Mx",
      "amount": "15600.00",
      "wht_amount": "450.00"
    }
  ],
  "withholding": [
    {
      "payee_name": "Demo Services Co., Ltd.",
      "payee_tax_id": "0999000000035",
      "payee_branch_no": "00000",
      "payee_address": "1 Example Road, Khlong Toei, Bangkok 10110",
      "payee_type": "company",
      "income_type": "service",
      "income_description": null,
      "gross_amount": "15000.00",
      "rate": "3",
      "wht_amount": "450.00",
      "certificate_number": "WHT-2026-0101",
      "return_form": "pnd53"
    }
  ],
  "attachments": [],
  "state": "recorded",
  "reversed_at": null,
  "reverse_reason": null,
  "created_at": "2026-10-31T16:55:02+07:00"
}

POST /v1/payments/{id}/reverse

Reverse a supplier payment

Second release (see Two releases): once the first release is live, this path answers 404 not_found until the second opens. Reverses a payment recorded by mistake. The bills it was allocated to owe the allocated amounts again, and its withholding entries no longer count. The payment stays visible with state: reversed. A payment dated in a closed period cannot be reversed (period_closed), nor one whose settlement SLF has already posted to your books (void_not_allowed). Withholding already in a return SLF has filed stays there; SLF handles that with you.

Parameters

Request body

application/json · VoidRequest

{
  "reason": "Transfer was rejected by the bank."
}

Responses

200 The reversed payment. · Payment

{
  "id": "pay_7Mv4Ys1Jn9Bc",
  "external_id": "AP-PAY-2026-10-0031",
  "pay_date": "2026-10-31",
  "method": "transfer",
  "bank_account_id": "bnk_5Qm2Rk8Lt3Vw",
  "reference": "TRF-20261031-0007",
  "allocations": [
    {
      "bill_id": "bil_5Tg9Hw2Lr6Mx",
      "amount": "15600.00",
      "wht_amount": "450.00"
    }
  ],
  "withholding": [
    {
      "payee_name": "Demo Services Co., Ltd.",
      "payee_tax_id": "0999000000035",
      "payee_branch_no": "00000",
      "payee_address": "1 Example Road, Khlong Toei, Bangkok 10110",
      "payee_type": "company",
      "income_type": "service",
      "income_description": null,
      "gross_amount": "15000.00",
      "rate": "3",
      "wht_amount": "450.00",
      "certificate_number": "WHT-2026-0101",
      "return_form": "pnd53"
    }
  ],
  "attachments": [],
  "state": "reversed",
  "reversed_at": "2026-11-01T10:12:45+07:00",
  "reverse_reason": "Transfer was rejected by the bank.",
  "created_at": "2026-10-31T16:55:02+07:00"
}

409 The payment is already reversed (already_voided), or it cannot be reversed now (void_not_allowed). · Error

{
  "error": {
    "code": "already_voided",
    "message": "This payment is already reversed.",
    "param": null,
    "details": [],
    "request_id": "req_2f7c4a9e1d5b8c36",
    "existing_id": null
  }
}

Errors specific to this endpoint

already_voided, void_not_allowed, period_closed. Common errors: see Error codes.

POST /v1/attachments

Upload an attachment

Uploads a file and attaches it to a sales document or receipt (to a bill or payment from the second release; until then reference_not_found). Send multipart/form-data with the fields of AttachmentUpload and one file; form fields the API does not know are ignored, and a second file is refused with validation_failed. The file's type is read from its content, not from its name or the media type you declare. Allowed types: PDF, JPEG, PNG and WebP, up to 10 MB; anything else is refused with 415 unsupported_media_type or 413 payload_too_large. HEIC is not accepted: convert such photos to JPEG first. A voided record takes no new attachments (validation_failed, invalid_value on /object_id). Your company may upload up to 1 GB or 1,000 files per day, Bangkok time; above that, uploads are refused with 429 rate_limited and Retry-After until midnight. If the same file (by SHA-256) is already attached to the same record, the existing attachment is returned with 200 instead of 201.

Parameters

Request body

multipart/form-data · AttachmentUpload

{
  "file": "(binary content of TIV-2026-0412.pdf)",
  "object_type": "sales_document",
  "object_id": "doc_9Rt3Vb6Nz1Hs",
  "kind": "document_copy"
}

Responses

201 The file was stored and attached. · Attachment

{
  "id": "att_2Bh5Rx8Fk3Wq",
  "object_type": "sales_document",
  "object_id": "doc_9Rt3Vb6Nz1Hs",
  "kind": "document_copy",
  "file_name": "TIV-2026-0412.pdf",
  "content_type": "application/pdf",
  "size": 184233,
  "sha256": "9f2b5c1e7a4d8f0c3b6e9a2d5c8f1b4e7a0d3c6f9b2e5a8d1c4f7b0e3a6d9c2f",
  "created_at": "2026-10-08T11:05:37+07:00"
}

200 The same file was already attached to this record; the existing attachment is returned. · Attachment

{
  "id": "att_2Bh5Rx8Fk3Wq",
  "object_type": "sales_document",
  "object_id": "doc_9Rt3Vb6Nz1Hs",
  "kind": "document_copy",
  "file_name": "TIV-2026-0412.pdf",
  "content_type": "application/pdf",
  "size": 184233,
  "sha256": "9f2b5c1e7a4d8f0c3b6e9a2d5c8f1b4e7a0d3c6f9b2e5a8d1c4f7b0e3a6d9c2f",
  "created_at": "2026-10-08T11:05:37+07:00"
}

413 The file is larger than 10 MB. · Error

{
  "error": {
    "code": "payload_too_large",
    "message": "The file is 14.2 MB; the limit is 10 MB.",
    "param": null,
    "details": [],
    "request_id": "req_4e9a2c7f1b5d8e36",
    "existing_id": null
  }
}

415 By its content, the file is not PDF, JPEG, PNG or WebP. · Error

{
  "error": {
    "code": "unsupported_media_type",
    "message": "Files of type application/zip cannot be attached.",
    "param": "/file",
    "details": [],
    "request_id": "req_7b3d1f8a4c6e2b95",
    "existing_id": null
  }
}

422 The record to attach to does not exist or is voided, or a field is invalid. · Error

{
  "error": {
    "code": "reference_not_found",
    "message": "No sales document doc_9Rt3Vb6Nz1Hx exists for your company.",
    "param": "/object_id",
    "details": [],
    "request_id": "req_2a8c5e1d9f4b7a63",
    "existing_id": null
  }
}

429 Your company's daily upload limit is reached. · Error

{
  "error": {
    "code": "rate_limited",
    "message": "Your company has uploaded 1,000 files today, the daily limit. Retry after midnight Bangkok time.",
    "param": null,
    "details": [],
    "request_id": "req_5d8b2f6a9c1e4d73",
    "existing_id": null
  }
}

Errors specific to this endpoint

reference_not_found. Common errors: see Error codes.

GET /v1/attachments

List attachments of a record

Returns the attachments of one record that were uploaded through the API, newest first. Files SLF attached itself are not listed.

Parameters

Responses

200 A page of attachments. · list of Attachment

{
  "data": [
    {
      "id": "att_2Bh5Rx8Fk3Wq",
      "object_type": "sales_document",
      "object_id": "doc_9Rt3Vb6Nz1Hs",
      "kind": "document_copy",
      "file_name": "TIV-2026-0412.pdf",
      "content_type": "application/pdf",
      "size": 184233,
      "sha256": "9f2b5c1e7a4d8f0c3b6e9a2d5c8f1b4e7a0d3c6f9b2e5a8d1c4f7b0e3a6d9c2f",
      "created_at": "2026-10-08T11:05:37+07:00"
    }
  ],
  "next_cursor": null
}

GET /v1/attachments/{id}

Get attachment details

Returns an attachment's details, without the file.

Parameters

Responses

200 The attachment's details. · Attachment

{
  "id": "att_2Bh5Rx8Fk3Wq",
  "object_type": "sales_document",
  "object_id": "doc_9Rt3Vb6Nz1Hs",
  "kind": "document_copy",
  "file_name": "TIV-2026-0412.pdf",
  "content_type": "application/pdf",
  "size": 184233,
  "sha256": "9f2b5c1e7a4d8f0c3b6e9a2d5c8f1b4e7a0d3c6f9b2e5a8d1c4f7b0e3a6d9c2f",
  "created_at": "2026-10-08T11:05:37+07:00"
}

GET /v1/attachments/{id}/content

Download an attachment

Returns the file itself.

Parameters

Responses

200 The file, with its content_type as the Content-Type header and its file_name in a Content-Disposition header. · the file itself (application/octet-stream)

GET /v1/periods/{month}

Get a month's totals

Returns the month's figures as SLF has recorded them, so you can compare them with your own system's totals. If they differ, contact SLF. All amounts are in THB. status shows whether SLF has filed the month's VAT return or closed the period. Sales lines SLF has not classified yet are counted in sales.unclassified_value, and sales records held back by SLF's arithmetic check in quarantined; neither is included in the other figures. For a company that is not VAT-registered, every VAT figure is zero. A month with no records returns zero totals.

Parameters

Responses

200 The month's figures. · Period

{
  "month": "2026-09",
  "status": "vat_filed",
  "filings": [
    {
      "form": "pp30",
      "filed": true
    },
    {
      "form": "pnd3",
      "filed": true
    },
    {
      "form": "pnd53",
      "filed": true
    },
    {
      "form": "pnd1",
      "filed": false
    }
  ],
  "sales": {
    "document_count": 64,
    "taxable_value": "412350.00",
    "zero_rated_value": "38900.00",
    "exempt_value": "0.00",
    "unclassified_value": "0.00",
    "vat": "28864.50"
  },
  "purchases": {
    "document_count": 41,
    "taxable_value": "158200.00",
    "vat": "11074.00"
  },
  "out_of_scope_value": "12750.00",
  "quarantined": {
    "count": 0,
    "value": "0.00"
  },
  "withholding": {
    "pnd3_amount": "1250.00",
    "pnd53_amount": "4830.00"
  }
}