Thailand's annual corporate income tax filing: what comes first

01It is not one form. It is a chain.

A lot of companies read the annual filing as "one income tax form at the end of the year". In practice, the same audited working papers feed two government departments and run through four checkpoints:

• Audit. The financial statements have to be audited.
• Annual corporate income tax return. Filed within 150 days of the end of the financial year, with the audited financial statements attached; what was already paid at the half-year prepayment is credited against it.
• Shareholders' meeting. Held within a set period after the year end, to consider the financial statements.
• Annual financial statements filed with the Department of Business Development (DBD). Completed within the prescribed period after the shareholders' meeting.

The four windows interlock. Two weeks late on the audit means two weeks late on the shareholders' meeting, and both filings behind it move with them — and each of them carries its own consequence for being late. So the real starting point of annual compliance is not counting back from the deadline. It is the auditor's schedule.

A practical warning. Audit capacity in Thailand is tight in year-end season, and companies with a 31 December year end all arrive at once. Agree the auditor and the slot before the year end, not after it. For the individual filings that run through the rest of the year, see the Thai filing calendar.

02What to finish in the three months

Working backwards from the deadline:

• Before the year end. Confirm the auditor and the slot. Put the year's open items in a list — unposted vouchers, open receivable and payable balances, the stocktake arrangements, the fixed asset count.
• First month after the year end. Close the books and issue management accounts. Reconcile the year's tax filings against the ledger: the numbers you filed month by month and the numbers on the books have to agree.
• Second month after the year end. Support the audit and respond to audit adjustments. In parallel, prepare the working papers for the book-to-tax differences the return will need.
• Third month after the year end. Sign off the audit report, prepare the shareholders' meeting papers, complete and review the return itself.

If this is your company's first year end in Thailand, it is also worth reading the traps a first year on the ground throws up.

03The three adjustments that go wrong most often

Three things cause more trouble in the annual return than anything else.

• Non-deductible items not added back. Some expenses go through the accounts as costs but are not deductible for tax, and have to be added back at the annual filing. If they are not collected separately during the year, hunting for them through the ledger at year end is slow and easy to get wrong. Set up separate analysis accounts in the chart of accounts for the common non-deductible items, so they are collected as they arise and can simply be read off at the year end.
• Deductions denied because the supporting document does not hold up. The expense is real and the payment was made, but the invoice is missing required particulars or is made out to the wrong party — and the deduction can be struck out. This is daily discipline, not something you can repair in the closing weeks.
• A company with exempt income that has not separated its accounts. If your company has promoted activities, exempt income and taxable income must be computed separately, and shared costs need an allocation basis that stands up and is applied consistently from year to year. Whatever cannot be separated is likely to be treated as taxable in full.

04Do not forget the half-year prepayment

Alongside the annual return there is a half-year corporate income tax prepayment, filed within the prescribed period after the first half of the year ends. It needs the first-half result and an estimate of the full-year profit. It attracts little attention, but in some circumstances an estimate that is too far off has consequences — this is not a number to put down at random. What is paid at the half year is credited at the annual filing.

05How to keep the chain from breaking

Two schedules are worth building. One is a backward-planned calendar of the year's checkpoints: take audit, the annual return, the shareholders' meeting and the accounts filing, work out the actual dates against your own year-end date, and leave a buffer in front of each. The other is a year-end adjustment list: book-to-tax differences, non-deductible items and the exempt-versus-taxable split, each with its data source and the person responsible.

Build both before the year end, and the whole year's compliance is simply working to the schedule. Build them after the year end, and it is a fire drill — once a year, every year.

The actual dates that follow from your own year-end date, which book-to-tax differences you need to adjust, and whether your basis for splitting exempt income holds up all have to be checked item by item against your accounting policies, your ledgers and the filings of previous years. What the monthly tax compliance engagement covers.