Summary information from the Revenue Department regarding "late tax filing, forgotten filing, or forgotten payment" for the 2025 tax year (filing in early 2026) is provided below to help you understand clearly and act correctly.
If you miss the normal tax filing deadlines—paper by 31 Mar 2026 and online by 8 Apr 2026—you can proceed as follows:
If you have not yet filed: you can immediately file retroactively through the online system.
If you filed but forgot to pay: 1. Log in to the Revenue Department's online system. 2. Go to the "Tax Payment" menu. 3. Click "Cancel previous return" that you filed. 4. Submit a "new return" and pay immediately in that process.
Late filing incurs extra costs payable along with any tax due, divided into two main parts:
Criminal fine (for late filing).
Length of delay. | Minimum fine rate. |
Late filing within 7 days. | Fine of 100 baht. |
Late filing over 7 days. | Fine of 200 baht. |
Note. | Maximum fine not exceeding 2,000 baht. |
Charged at 1.5% per month of the tax due.
Any fraction of a month counts as a full month.
Counted from the day after the deadline until the actual payment date.
To be clear, remember to meet these deadlines to avoid future fines:
Paper filing: by 31 March 2026.
Online filing: by 8 April 2026.
If you need to file retroactively, it is recommended to prepare all income documents and deduction rights before accessing the system to ensure accurate re-filing and calculation of additional charges.