Annual audit in Thailand: 2026 deadlines, process and penalties

Every company registered in Thailand must have its annual financial statements audited by a Certified Public Accountant licensed by the Federation of Accounting Professions. The rule covers every limited company and most registered partnerships; there is no exemption merely because a business is small, loss-making or dormant. Three statutory deadlines then follow the financial year-end: the annual general meeting (AGM) must approve the audited statements within four months, the approved statements must reach the Department of Business Development (DBD) within one month of the AGM, and the PND.50 corporate income-tax return must reach the Revenue Department within 150 days.

For the 31 December year-end used by most Thai companies, that means an AGM by 30 April, DBD e-Filing by 31 May at the latest, and a PND.50 by around 30 May — plus the Revenue Department's eight-day extension for e-filing, where the announcement in force covers the due date. Miss those dates and penalties follow. Which of them reach a director personally depends on the offence: the fine for a late PND.50 falls on the company as taxpayer, while several offences under the company and accounting legislation name the directors or the person responsible.

As of August 2026, the next deadline for a calendar-year company is 31 August: the PND.51 half-year tax return. The next full audit cycle — for the 31 December 2026 year-end — runs from January to May 2027 on the timetable below. For the preparation errors that most often cause missed deadlines, read our companion piece on the five common audit-preparation mistakes.

Who must be audited in Thailand?

Every Thai limited company, without exception. Turnover, headcount and activity are irrelevant: a company that recorded no transactions all year still needs a full CPA audit, an AGM and the same filings. Registered partnerships are audited too, with one narrow relaxation — a small registered partnership with capital up to THB 5 million and revenue and assets each up to THB 30 million is excused the CPA audit, though its tax return still needs certification by a qualified auditor, which may be a CPA or a Tax Auditor depending on which criteria it meets. A limited company never qualifies for that relaxation.

The auditor must be independent and hold a CPA licence from the Federation of Accounting Professions — a company cannot audit itself, and directors cannot approve their own accounts in place of an auditor. The audit produces a signed opinion on whether the statements give a true and fair view; that opinion is what the AGM approves and the authorities receive.

What are the deadlines for a 31 December year-end?

For a 31 December 2026 year-end, the cycle is:

• 31 December 2026 — close the books: final entries, accruals, depreciation and tax provisions are booked, and every bank account is reconciled to the ledger.
• January to March 2027 — audit fieldwork: convention rather than law, but auditors are at their busiest in these months, and a late start squeezes every deadline behind it.
• By 30 April 2027 — hold the AGM: the meeting must approve the audited statements within four months of year-end, on at least seven days' notice to shareholders.
• Within 14 days of the AGM — file the BOJ.5: the updated shareholder list runs on its own clock and carries its own fine. It is a separate filing, and lodging the financial statements does not discharge it, even where both go in the same week.
• Within one month of the AGM — file the audited statements with the DBD: submit them electronically through the DBD e-Filing system in XBRL format. An AGM on 30 April makes the deadline 31 May 2027. Entities that hold no AGM — registered partnerships and foreign-company branches — file within five months of year-end instead.
• Within 150 days of year-end — file the PND.50: section 68 of the Revenue Code sets the deadline at 150 days, so for a 31 December 2026 year-end the 150th day is 30 May 2027 — a Sunday, which moves the deadline to the next working day. Check the 2027 public-holiday calendar rather than assuming 31 May. Revenue Department e-filing currently adds around eight days, but that extension scheme is announced only to 31 January 2027 — confirm it before relying on it for 2027 filings.
• By 31 August — file the PND.51: the half-year return lands mid-cycle every year — due 31 August 2026 for the current calendar year, or around 8 September if e-filed.

The deadlines are linked. Without a signed audit there is nothing for the AGM to approve; without an AGM there is nothing to file at the DBD; and the PND.50 must reconcile to the audited numbers. One slow link drags everything behind it.

How does the audit process work, step by step?

• Close and reconcile: the books are closed, bank accounts reconciled, and year-end entries booked.
• Hand over the audit pack: the auditor receives the ledger, trial balance, reconciliations, supporting schedules and draft financial statements as one complete set.
• Fieldwork and queries: the auditor tests the figures against bank statements, contracts, invoices and stock records, and raises questions.
• Adjustments and signing: agreed audit adjustments are booked, the auditor signs the report, and a director signs the financial statements.
• Tax, AGM, filings: any corporate income tax due is settled, the AGM approves the statements, and the BOJ.5, the DBD filing and the PND.50 are completed by their respective deadlines.

The audit itself must be performed by an independent CPA; everything around it — the pack, the auditor liaison, the filings — can be delegated. That coordination is what our annual audit service covers.

What does the auditor need, and how long does an audit take with complete records?

The auditor will ask for three groups of material:

• The year's records and monthly returns: income and expense records together with the PND 1, 3 and 53 withholding-tax filings, the PP30 and PP36 VAT returns, and the social security submissions.
• Verification documents: bank statements for every account held during the year, inventory listings and stock cards where the company holds stock, the lease for the company's premises, and copies of any land title deeds it owns.
• Continuity items: the prior year's audited statements and PND 50, the general ledger, trial balance and fixed-asset register, and the PND 51 — plus the company seal, where the company uses one.

How long fieldwork takes depends on size, complexity, the risks identified and the state of the records. In our experience, a small or medium company with that pack complete and reconciled takes weeks rather than months, and companies that start in January are finished before April. What stretches the timetable is rarely the audit itself: unreconciled bank accounts, missing documents, an inventory nobody counted, or schedules rebuilt mid-audit.

NPAE or PAE: which accounting standard applies?

Most private Thai companies report under TFRS for Non-Publicly Accountable Entities (NPAEs), a simplified framework for companies that are not listed, are not regulated financial institutions and do not issue securities to the public. Publicly accountable entities (PAEs) — listed companies, banks, insurers — report under full Thai Financial Reporting Standards, which track IFRS. The audit is conducted under the Thai Standards on Auditing either way, but the two frameworks differ in accounting principle — recognition, measurement, presentation and disclosure — not merely in how much has to be disclosed. The Federation of Accounting Professions publishes a summary of the significant differences between them.

Who must file the half-year PND.51?

Every company subject to corporate income tax on net profit must file — including a company expecting a loss. The company estimates its full-year net profit, calculates the tax and pays half of it within two months of the end of the first six months of the accounting period: 31 August for a calendar-year company, or around 8 September if e-filed. Section 67 bis excepts both a first and a final accounting period that runs for less than twelve months. A defined group pays on actual first-half profit instead of an estimate: listed companies, commercial banks, finance companies, securities companies, credit foncier companies, and any other juristic person the Director-General prescribes.

The estimate has teeth: understate full-year net profit by more than 25% of the actual result, without reasonable cause, and section 67 ter imposes a 20% surcharge — calculated on the tax underpaid, not on the amount of profit understated. What counts as reasonable cause comes from Revenue Department Instruction Por. 152/2558, and the safe harbour there is a tax test rather than a profit test: half-year tax paid of at least half the corporate income tax filed for the previous accounting period. The instruction also covers the company that estimates net profit at no less than last year's but pays under half the tax because of an exemption or a reduced rate. The mechanics are on our half-year report page.

What are the penalties, and which authority fines what?

Penalties imposed by the DBD

• No AGM within four months: fines of up to THB 20,000 on the company and up to THB 50,000 on the directors personally. Those are statutory ceilings; the amounts actually levied are discretionary.
• Late financial statements: the Accounting Act caps the penalty at THB 50,000 on the company plus THB 50,000 on the managing director. The amounts levied in practice sit well below that and escalate with the delay: THB 1,000 each on the company and the managing director for filings up to two months late; THB 4,000 each for delays of two to four months; and THB 6,000 each for delays beyond four months or where nothing is filed. Those are the figures seen in practice, not a current published schedule — the DBD maintains its own fine-rate table for late financial statements, and what applies is the rate in force on the date of the offence.
• Late BOJ.5: a separate fine on the directors of up to THB 10,000, commonly THB 2,000 in practice, subject to the same caveat.

Penalties imposed by the Revenue Department

• Late PND.50: a fine of up to THB 2,000, plus a surcharge of 1.5% per month on any unpaid tax — a part month counts as a full month. Section 27 of the Revenue Code caps the accrued surcharge at the amount of the tax itself.
• Assessment penalties: if the Revenue Department assesses you before you file voluntarily, a penalty of 100% of the tax shortfall applies to an incorrect return — 200% where no return was filed at all.
• No auditable records: section 71(1) lets an assessment officer tax the company at 5% of gross receipts or gross sales before deducting any expenses, whichever of the two is higher. It does not follow automatically from records an auditor finds weak — the section applies in defined cases, including failure to file the return, failure to keep the accounts the law requires, and failure to produce accounts or documents when the officer calls for them. For a low-margin business the result is often more than the year's real profit.
• Short PND.51 estimate: the 20% surcharge on the tax underpaid, described above.

The cost of repeated non-filing

Three consecutive years of non-filing gives the DBD grounds to treat the company as no longer carrying on business and to start strike-off proceedings. It is a process rather than an automatic event on the third anniversary: the DBD notifies the company and publishes notice, and the company can respond or bring its filings up to date first. If the strike-off completes, the company loses its legal personality — and anything that depended on the company existing, from work permits and visa extensions to bank facilities, then falls to be reassessed under the immigration, labour or contractual rules that govern it, rather than all lapsing on the same day. The filing record also follows the company into credit checks and any future sale.

What happens if you miss the AGM window?

The offence is complete the moment four months pass without a meeting, and the fine exposure above applies. Hold the AGM as soon as possible anyway. The one-month DBD filing clock runs from the actual meeting date, so a prompt late AGM keeps the financial statements from going late as well; the BOJ.5's 14-day clock likewise runs from the real meeting. And the PND.50's 150-day clock runs from year-end regardless — a delayed meeting is no reason to let the tax return slip too.

Why do foreign-owned companies slip?

The pattern we see most often in our own files is not negligence but geography. Source documents sit with a head office abroad and arrive in batches; the group's reporting calendar puts the Thai subsidiary at the back of the queue; the parent's finance team wants to review the file in English before a director signs; and the signing director is rarely in Thailand in the week it matters. Each step is reasonable — together they consume the four-month window.

The fix is to plan backwards from 30 April: audit pack complete by the end of February, bilingual schedules ready for head-office review, auditor queries answered in days, and the AGM booked for early April rather than the deadline itself.

What should you do if you are already late?

Move in sequence, and do not wait for a warning letter:

• Rebuild the books first: nothing can be signed until the accounts are auditable. If the bookkeeping is behind, reconstruction with professional bookkeeping support is step one.
• Audit, then AGM, then filings: complete the audit, hold the AGM now, file the BOJ.5 within 14 days and the statements with the DBD within one month of the meeting, and pay the settlement fine.
• File the PND.50 voluntarily: filing late of your own accord costs the small fine plus the 1.5% monthly surcharge on unpaid tax — a surcharge that cannot exceed the tax itself, so it reaches its ceiling after about five and a half years and stops there. Waiting for an assessment adds the 100% or 200% penalty on top.
• Check the register: if filings have been missed for years, confirm the company has not been flagged for strike-off. A company already struck off can only be restored by court order, and the application cannot be made more than ten years after the date of the strike-off.

Back-filing several years at once is work we do regularly, and in the cases we handle the fines come out smaller than owners expect — far smaller than the cost of a strike-off. If year-round compliance is the underlying problem, a combined accounting and tax package keeps the books, the monthly returns and the audit calendar on one track.

---

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.