What Documents Your Thai Accountant Needs Each Month

Working with a Thai accountant goes more smoothly when you know what to bring to the table each month. Many business owners in Thailand, especially those running foreign-owned companies or small operations in places like Koh Samui, lose time and money simply because documents arrive late, incomplete, or in the wrong format. This guide walks you through exactly what your accountant needs from you on a monthly basis, why each item matters, and how to build a simple routine that keeps your compliance on track.

Sales Records and Tax Invoices Issued

Your accountant needs a complete record of every sale your business made during the month. This means copies of all tax invoices you issued to customers, along with any receipts or sales summaries if you operate a retail or hospitality business. In Thailand, VAT-registered businesses are required to issue tax invoices that meet specific legal requirements, so your accountant will check that these are correctly formatted before using them to prepare your VAT return.

If your business uses accounting software or a point-of-sale system, a monthly sales report exported from that system is usually sufficient, as long as it includes the date, amount, VAT amount, and customer details where applicable. The key is consistency. Send everything from that month, not just selected invoices.

Purchase Invoices and Expense Receipts

Every purchase your business made during the month needs to be documented. This includes supplier invoices, utility bills, rent agreements or rent receipts, office supply receipts, and any other business expenses. In Thailand, these documents are not just useful for understanding your costs. They are the basis for claiming input VAT and for recording deductible expenses that reduce your corporate tax liability.

A common problem is that receipts get lost or arrive in a disorganised pile. A practical solution is to photograph receipts as soon as you receive them and store them in a dedicated folder, either physical or digital, labelled by month. Your accountant will need the original or a clear copy, and for VAT purposes the document generally needs to show the seller's tax ID number and your company's name and tax ID. Informal receipts without these details cannot be used for VAT input claims.

Bank Statements for All Business Accounts

Your accountant needs the bank statement for every business account your company holds, covering the full calendar month. This includes current accounts, savings accounts used for business purposes, and any accounts held at different banks. Bank statements allow your accountant to reconcile your records, spot transactions that were not captured by invoices, and ensure that what appears in your books matches what actually moved through your accounts.

Download or request statements as soon as they are available after month-end. If your bank provides PDF statements through online banking, this is usually the quickest option. Make sure the statement shows the account holder name, account number, and all transactions with dates and references. Statements that cut off mid-month are not useful for monthly reporting and will slow your accountant down.

Payroll Information and Employee Records

If you employ staff, your accountant needs payroll data each month to prepare the social security contributions filing and, where relevant, the personal income tax withholding return. You will typically need to provide a list of employees, their salaries or wages for that month, any overtime or bonus payments, and details of any new hires or staff who left during the month.

In Thailand, employers must file and pay social security contributions by the 15th of the following month, so this information needs to reach your accountant quickly after the month closes. If your workforce changes frequently, as is common in hospitality and tourism businesses on Koh Samui, staying on top of this monthly is especially important. Errors in payroll filings can result in penalties that are straightforward to avoid with timely, accurate information.

Withholding Tax Certificates and Third-Party Payments

Many businesses in Thailand are required to withhold tax when they pay for certain services, such as professional fees, rent, or transport. When you make these payments, you deduct a percentage, remit it to the Revenue Department, and issue the service provider with a withholding tax certificate. Your accountant needs records of all such payments made during the month so they can prepare the monthly withholding tax return, known as the PND 1, PND 3, or PND 53 depending on who was paid.

If you are unsure which of your payments are subject to withholding tax, your accountant can advise you on this. However, it is your responsibility to track these payments and inform your accountant of them. Missed withholding tax filings are one of the more common compliance issues for small businesses in Thailand, and the penalties and surcharges add up quickly.

Any Other Changes or One-Off Transactions

Beyond the regular monthly documents, you should flag anything unusual that happened during the month. This might include a large one-off purchase, a loan taken out or repaid, an asset bought or sold, a refund issued to a customer, money transferred between accounts, or any transaction that falls outside your normal business activity. These items require specific accounting treatment and your accountant cannot handle them correctly if they do not know about them.

It is also worth informing your accountant if you received any correspondence from the Revenue Department, the Social Security Office, or the Department of Business Development during the month. Even if a letter seems routine or you are unsure of its significance, your accountant will want to see it. Keeping your accountant informed of the full picture each month is what allows them to keep your records accurate and your business compliant throughout the year.

Building a Simple Monthly Routine

The businesses that have the fewest accounting problems are usually the ones that treat document collection as a habit rather than a last-minute task. Set a date shortly after month-end, perhaps the first or second working day, to gather and send everything on this list. If you work with SLF Accounting, we can provide you with a simple checklist tailored to your specific business type so you always know what is expected and when. Getting into a rhythm with your accountant not only keeps your filings on time, it gives you a cleaner view of how your business is actually performing.