ACCOUNTING SERVICES / TAX
Corporate income tax is calculated from taxable profit, which can differ from the profit shown in the financial statements. Preparing the return means connecting the accounts to a documented tax computation, checking eligibility for the applicable rates and reconciling available credits.
Pimaccounting can discuss annual PND 50 preparation, the half-year PND 51 process and the records needed to support the calculation. The company’s accounting period, activity, ownership, incentives and transaction profile should be reviewed before selecting the treatment.
Information reviewed 13 November 2026 · Pimaccounting
Corporate tax rates and SME bands
The general corporate income tax rate is 20% of taxable net profit. Qualifying SMEs with paid-up capital not exceeding THB 5 million at the end of the accounting period and income from sales of goods and services not exceeding THB 30 million can fall within the reduced bands below. Confirm all eligibility conditions for the actual period. Revenue Department rates and conditions.
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| Taxable profit band for an eligible SME | Rate on that band |
|---|---|
| Up to THB 300,000 | Exempt |
| Over THB 300,000 up to THB 3 million | 15% |
| Over THB 3 million | 20% |
These are marginal bands, not a single rate applied to all profit. For illustration, an otherwise eligible SME with THB 1 million taxable profit would have THB 700,000 in the 15% band, producing THB 105,000 tax before credits. A company taxed at the general 20% rate on the same taxable profit would have THB 200,000 before credits. The example assumes no special regime or other adjustment.
From accounting profit to taxable profit
Begin with a reconciled trial balance and the financial statements. Identify items whose accounting treatment differs from the tax rules. The working paper should show the original amount, adjustment, explanation and supporting authority or document, allowing another reviewer to follow the calculation.
- Review expenses for business purpose, documentation and any statutory restrictions.
- Compare accounting depreciation with the tax treatment of assets.
- Examine provisions, accruals, bad debts and timing differences.
- Review related-party transactions, financing costs and unusual receipts.
- Check the availability and treatment of brought-forward tax losses.
- Separate income or expenditure covered by a valid incentive where required.
A tax adjustment should not erase the underlying accounting entry. Keep a bridge between the financial statements and the return. Changes identified during audit may require the tax computation to be revised before filing.
PND 50 and PND 51 serve different purposes
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| Return | Main purpose | General timing |
|---|---|---|
| PND 50 | Annual corporate income tax calculation and reconciliation. | Within 150 days after the accounting year-end. |
| PND 51 | Half-year corporate tax prepayment where applicable. | Within two months after the first six months of the accounting period. |
The Revenue Department filing overview explains these baselines. Confirm short-period and first-year treatment, the calculation method applicable to the entity and any current filing extension. Check the official calendar for the actual deadline and payment conditions.
For a company using an estimated annual-profit basis for PND 51, prepare a credible full-year forecast rather than simply copying last year. Consider contracts, seasonality, cost changes and significant transactions. Review an unusually low estimate with the adviser because an inadequate estimate can have consequences under the tax rules.
Reconcile payments and withholding credits
Maintain a schedule of tax already paid and withholding credits supported by the appropriate evidence. Match the company name, tax number, income period and amounts to the relevant records. A customer’s short payment alone is not sufficient evidence that tax was correctly withheld and remitted.
Reconcile the half-year payment to its official receipt. Identify any carried-forward credit or refund claim and retain the supporting calculation. If a refund is expected, prepare for the possibility of a request for documents rather than treating the submission as confirmation that the amount has been accepted.
Keep the tax payable balance in the accounts consistent with the computation and subsequent payment. Differences between a provisional year-end estimate and the final calculation should be explained and posted through the appropriate review process.
BOI projects, related parties and overseas activity
BOI promotion does not mean every receipt of the company is exempt. Review the certificate, eligible project, incentive period, caps and conditions. The BOI requires the accounting structure to separate revenue and expenses for relevant projects benefiting from corporate tax exemption. Its tax-incentive guidance also sets out application and supporting-report requirements.
Companies with promoted and non-promoted activities need a documented allocation method and a reconciliation to the entity-level accounts. Do not assume that a new product, contract or location is covered simply because an existing project has a promotion certificate.
Overseas income, intercompany charges, royalties, loans and restructurings can require further tax and treaty analysis. Large multinational groups may have additional reporting or tax regimes beyond ordinary local SME compliance. Identify these features at the start of the engagement so they can be scoped appropriately.
Prepare the annual tax file
Collect the financial statements and trial balance, detailed ledgers, fixed-asset schedule, loan agreements, material contracts, tax-loss schedules, withholding evidence and prior returns. Include PND 51 calculations and receipts, BOI documents where relevant, and a list of unusual or disputed transactions.
Agree who prepares the computation, resolves questions, approves the return, submits it and funds the payment. Retain the final version and acknowledgement together. After filing, reconcile the tax accounts and carry forward any remaining credits or review points with clear supporting schedules.
Corporate income tax questions
Is the tax calculated on sales revenue?
For the ordinary net-profit regime, the calculation starts from taxable profit, not simply sales. Revenue remains important for matters such as SME eligibility and other tax obligations.
Does an accounting loss mean no return is required?
Do not assume that. A filing obligation can remain, and taxable profit may differ from the accounting result. Review the return and any loss position separately.
Is PND 51 an additional tax on top of annual tax?
It is a half-year prepayment where applicable and is reconciled against the annual liability. Keep the calculation and payment evidence for the PND 50 process.
Do all small companies qualify for SME rates?
No. The relevant capital and revenue conditions and the company’s circumstances must be checked for the period. “Small business” is not sufficient evidence of eligibility.
Does the annual audit include the corporate tax return?
Only if separately included in the agreed work. Audit, financial-statement preparation and tax computation have different purposes and responsibilities.
Official references and further reading
- Revenue Department — corporate income tax rates and SME bands (Thai)
- Revenue Department — corporate income tax filing
- Revenue Department — current tax filing calendar
- BOI — corporate income tax incentive conditions
References checked on 13 November 2026. Current legislation, official notices and the facts of the case take precedence over older summaries. This guide provides general information; confirm the applicable treatment and engagement scope before acting.
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