Five common mistakes in Thai annual-audit preparation

Every Thai limited company must have its annual financial statements audited by a licensed CPA — a certified public accountant authorised to sign audits in Thailand. There is no small-company or dormant-company exception: if the company exists on the register, it gets audited every year. The law's only relaxation covers small registered partnerships (capital up to THB 5 million, revenue and assets each up to THB 30 million) — and even they still need a Tax Auditor's certification for the Revenue Department. A limited company never qualifies.

In practice, most companies with a 31 December year-end close their books in December and host the auditor's fieldwork between January and March. That timetable is convention, not law. The deadlines that actually bite come in April, May and June — and missing them brings fines on the company and on the directors personally.

Below: the compliance calendar, the five mistakes we see most often, the dormant-company trap, the penalties, and a quarterly routine that keeps audit season boring.

The annual compliance calendar (31 December year-end)

Four deadlines anchor the whole season. Using a 31 December 2025 year-end as the example, as of June 2026:

• AGM within 4 months of year-end — by 30 April 2026. The annual general meeting of shareholders approves the audited financial statements. Notice must reach shareholders at least 7 days before, by post with acknowledgement of receipt or in person. Since a law change effective 7 February 2023, newspaper publication of the notice is no longer required — unless the company has bearer shares or its own articles of association still demand it.
• Updated shareholder list (form BOJ.5) within 14 days of the AGM. The old habit of filing it together with the financial statements is no longer accepted; it runs on its own 14-day clock and carries its own fine.
• Audited financial statements to the DBD within 1 month of the AGM. The DBD (Department of Business Development) requires a limited company to file within 1 month of the meeting that approved the statements; entities that hold no AGM — registered partnerships and foreign-company branches — file within 5 months of year-end instead. For the 31 December 2025 year-end the government asked entities to e-file by 2 June 2026 — an administrative date, not a new statutory deadline.
• PND.50 corporate income tax return within 150 days of year-end. Around 30 May for a calendar-year company — currently extended by 8 days (to 158) for Revenue Department e-filing.

The deadlines chain: no finished audit, no AGM; no AGM, nothing to file at the DBD; and the PND.50 must match the audited numbers. One slow link delays everything behind it.

Mistake 1: messy or incomplete bookkeeping

The most common problem is the simplest: the books do not match reality. Bank accounts are unreconciled — the ledger says one balance, the bank statement another — and source documents (invoices, receipts, contracts) are missing for part of the year.

An auditor cannot sign what they cannot verify. At best you pay extra fees while records are reconstructed. At worst there are no auditable accounts at all — and then the Revenue Department can assess corporate income tax at 5% of gross receipts, before deducting a single baht of expenses. For a low-margin business that can exceed the year's real profit.

VAT-registered companies (mandatory once annual turnover passes THB 1.8 million) feel this fastest: the monthly PP.30 VAT return — due by the 15th of the following month, or the 23rd via e-filing — must tie to the same books. The fix: reconcile every bank account monthly and file documents as you go. If nobody in-house does this reliably, outsourced bookkeeping costs far less than an audit rescue in February.

Mistake 2: interest-free loans to (or from) directors

In owner-managed companies, money moves between the company and its directors constantly — the owner covers a supplier invoice personally, or borrows from the company. Each movement is a loan in the eyes of the auditor and the Revenue Department.

The trap sits in Section 65 bis (4) of the Revenue Code: lend money interest-free or below market rate without reasonable cause, and the assessment officer can impute “deemed interest” — taxing the company on interest income it never received. The benchmark is the fixed-deposit rate where the company lent its own funds, and no lower than its own borrowing rate where it on-lent borrowed money.

The fix: document every director or shareholder loan with a written agreement, charge a defensible market rate, and where possible clear the balances before year-end.

Mistake 3: weak inventory records and no year-end count

If you sell goods and you are VAT-registered, you must keep stock cards — goods and inventory reports in the Revenue Department's prescribed format, updated within 3 working days of each movement. Many trading companies discover at audit time that nobody has maintained them.

The consequences are harsh. An unexplained shortage at the year-end count — stock the records say you hold but the warehouse doesn't — is a deemed sale: VAT is charged on the missing goods at market price, and the same amount is added to taxable income, unless you can evidence what happened (a police report for theft, say).

And if no physical count happens at year-end, the auditor cannot verify the inventory figure and must qualify the opinion — a warning flag on the financial statements that banks and counterparties can see. Book the count for the last days of December and invite the auditor to observe.

Mistake 4: ignoring related-party and transfer pricing rules

Two separate obligations get confused here. First, the disclosure form: companies with annual revenue of THB 200 million or more must file a transfer pricing disclosure form with the PND.50 — even in a year with zero related-party transactions. Failure or inaccuracy carries a penalty of up to THB 200,000.

Second — the part smaller companies miss — staying under THB 200 million does not make related-party rules disappear. Balances with related parties (broadly, 50%-plus shareholding or control links) must still be disclosed in the audited financial statements whatever your size, and pricing between related companies must still hold up at arm's length under Section 65 bis.

For larger groups there is a long tail: the Revenue Department can demand full transfer pricing documentation up to 5 years after filing, typically on a 60-day response window. Build the related-party schedule alongside the bookkeeping all year.

Mistake 5: withholding tax that doesn't match the books

Thai withholding tax (WHT) makes every paying company a tax collector: you deduct tax at source on services, rent, dividends and more, then remit it monthly on form PND.3 (payments to individuals) or PND.53 (payments to companies), due by the 7th of the following month, or the 15th via e-filing. Rates vary by payment type — 3% on service fees paid to companies, 5% on several payments to individuals, 10% on dividends — so there is no single rate to memorise.

The audit-season problem is mismatch. The Revenue Department routinely cross-checks your WHT filings against the expenses booked in the ledger and reported in the PND.50 and VAT returns. Expenses with no matching WHT filing are a classic audit trigger, and shortfalls accrue a 1.5%-per-month surcharge until paid.

The fix is a monthly habit: tie each month's PND.3/53 filings to the expense ledger before moving on. Twelve small reconciliations beat one impossible one.

The sixth trap: the “dormant” company nobody files for

“The company didn't trade this year, so there's nothing to file” is one of the most expensive sentences in Thai compliance. A dormant company has exactly the same obligations as an active one: CPA audit, AGM within four months, BOJ.5, DBD filing and PND.50 — every year, even with zero revenue.

Neglect compounds quietly. After three consecutive years of non-filing, the DBD can presume the company defunct and strike it off the register. The company loses its legal status — and with it everything that depended on it existing, including attached work permits and visas.

If you bought a villa through a Thai company in 2019 and it has been “sleeping” since, check now whether its financial statements have actually been filed each year — and read our note on company property structures.

What the penalties actually cost

As of June 2026, the layered penalty picture looks like this:

• No AGM within 4 months: fines of up to THB 20,000 on the company and up to THB 50,000 on the directors — personally. Actual amounts are discretionary; those are the statutory ceilings.
• Late financial statements at the DBD: escalating fines on both the company and the managing director — commonly THB 1,000 each up to 2 months late, THB 4,000 each at 2–4 months, THB 6,000 each beyond — capped by the Accounting Act at THB 50,000 on the company plus THB 50,000 on the managing director.
• Late BOJ.5 shareholder list: a separate fine on its own 14-day deadline.
• Late PND.50: a fine of up to THB 2,000, plus a surcharge of 1.5% per month on any unpaid tax. If the Revenue Department later assesses you, a separate penalty is added on top: 100% of the tax shortfall for an incorrect return — or 200% where no return was filed at all.
• No auditable records: assessment at 5% of gross income, before any expense deduction.
• Three years of non-filing: strike-off from the register, with the knock-on loss of dependent visas and work permits.

These fines stack — and the filing record follows the company into bank-credit checks, immigration renewals and any future sale.

How to prepare: a quarter-by-quarter routine

Companies that sail through their audit don't do anything heroic in January. They do small things all year:

• Every month: reconcile every bank account; file PP.30 (if VAT-registered) and PND.3/53 on time; tie the WHT filed to the expenses booked; archive invoices and receipts as they happen.
• Q1 (January–March): host the auditor's fieldwork on last year's accounts, answer queries quickly, and fix the AGM date well ahead of 30 April.
• Q2 (April–June): hold the AGM, file the BOJ.5 within 14 days, file the audited statements with the DBD within one month, and file the PND.50 within 150 days of year-end.
• Q3 (July–September): run a mid-year hard close and file the PND.51 half-year tax return, due within 2 months of the half-year end — end of August for calendar-year companies. Estimate carefully: understating the year's profit by more than 25% of the actual result, without reasonable cause, triggers a 20% surcharge on the shortfall. Refresh the fixed-asset register and stock cards while you're in the numbers.
• Q4 (October–December): clear or document director loans, finalise the related-party schedule, agree the audit timetable and fee, and book the year-end physical inventory count — with the auditor invited to observe.

If that list is more than your in-house team can absorb, this is precisely what a combined accounting and tax package or a standalone annual audit engagement is built to carry.

---

This article is general guidance — not legal or tax advice. If you'd like a scoped opinion on how it applies to your specific situation, contact our team.