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Late filing fine and surcharge calculator

Quick answer

The Revenue Code surcharge runs at 1.5% per started month of the tax payable and in total cannot exceed that tax. The criminal fine is charged per return — up to THB 500 for PP.30 and THB 2,000 for PND.50. Unremitted social security instead carries 2% per month with no equivalent ceiling.

Steps at a glance

  1. List which returns are outstanding
  2. Establish the tax for each period
  3. Count the months of delay
  4. Check the result against your source documents before filing.

What to prepare

  • The base amount from a tax invoice, bill or payslip.
  • The rate or income category that applies to the item.
  • Whether the entity is VAT-registered.
  • The tax period or month you are calculating.

Need a scope assessment? Describe the accounting or tax issue, relevant periods and due dates so the checks, required records and responsibilities can be clarified before a meeting.

Discuss your scope

Filed up to seven days late the fine is THB 300, beyond that THB 500 per return, and where tax is payable a separate section 89 penalty applies.

Tax payable for the period
100,000 THB
Surcharge at 1.5% per month × 3
4,500 THB
Criminal fine per return (maximum)
500 THB
Estimated amount to settle
105,000 THB
Ceiling note
Ceiling not reached yet

Figures are planning estimates, not tax advice. Have an accountant or CPA review your supporting documents before filing.

Hands comparing receipts beside a calculator and laptop; not Thai tax invoices
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Formula used

Surcharge = tax payable × 1.5% × months late (capped at the tax) · Total = tax + surcharge + per-return fine

How to use it and file correctly

  1. 1

    List which returns are outstanding

    Pull the filing history from Revenue Department e-Filing and the Social Security e-Service, then list every period with no proof of submission.

  2. 2

    Establish the tax for each period

    Work out the tax payable for that period from the underlying documents first — the surcharge is computed on tax, not on sales or payments.

  3. 3

    Count the months of delay

    Count from the due date to the day you will actually file; a part month counts as a whole one, so filing this month always costs less than waiting.

  4. 4

    File the oldest period first

    Submit the back filings in period order so input-tax and credit carry-forwards stay continuous, then settle the fines with the returns.

Common pitfalls

  • Never filing is treated differently from filing late: an assessment officer may assess the tax themselves with a penalty of one or two times the shortfall.

  • The statutory surcharge cannot be reduced, but certain penalties can be abated under regulation when you come forward before an audit begins.

  • The figures here are a planning estimate; the amount actually collected is determined by the officer on the day the return is submitted.

Frequently asked questions

Is the 1.5% monthly surcharge capped?

It accrues until payment but in total cannot exceed the tax payable for that period, so after roughly 67 months it stops growing.

Any penalty for a late nil return?

Yes — the criminal fine attaches to the late return itself regardless of tax, though the surcharge is zero when no tax is due.

Where to start on several back years?

Start from the oldest period and close that year's books first; one wrong opening balance drags the error through every later year.

Where is the fine paid?

It is paid with the return at the area Revenue Branch Office; back filings that the online system will not accept are submitted on paper and settled there.

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