# What is P.N.D.51 and how much do I pay?

Last updated: 25 October 2026
Country: Thailand
Category: tax

**Quick answer:** P.N.D.51 is the half-year corporate tax return. It is due within two months after the first six months (31 August for a calendar year), usually on half of the profit you estimate for the full year.

## Detailed explanation

## What it is

A prepayment of corporate income tax for the current year. It is credited against the annual P.N.D.50.

## How much

Most companies pay on half of the estimated full-year profit. Some companies, such as listed companies, pay on the actual six-month result. The Revenue Department allows a 25% margin of error on the estimate and charges a surcharge if the estimate falls short by more.

## When

Within two months after the first six months: 31 August for a calendar year. Online filing gives 8 more days.

## How AccountsOS helps

Finn shows the six-month result from your ledger and asks you before it estimates the full year.

Source: https://www.rd.go.th/english/6044.html

## Real-world examples

### Steady business

Expected full-year profit 2 million baht. P.N.D.51 is worked out on 1 million baht.

## Common mistakes to avoid

- Estimating far below the real result
- Forgetting to credit P.N.D.51 on P.N.D.50

## Frequently asked questions

### Do new companies file P.N.D.51?

Ask your accountant: the rule turns on the length of the accounting period.

## Practical tips

- Revisit the estimate after a strong first half.

## Related questions

- [When is the P.N.D.50 corporate tax return due in Thailand?](https://accounts-os.com/th/questions/when-is-pnd50-due-in-thailand)