The Mid-Year Tax Estimate (PND.51)
Every Thai company must estimate their full-year net profit halfway through the year and pay corporate tax on it. For companies with a January-December fiscal year, the deadline is August 31st.
You pay 50% of the estimated annual tax as an advance payment. This gets credited against your actual annual tax bill when you file PND.50 at year-end. If you overpaid, the excess becomes a tax credit or refund.
The 25% Underestimation Trap
If your actual annual profit turns out to be more than 25% higher than your estimate, the Revenue Department charges a 20% surcharge on the shortfall.
Real example: you estimate 1 million THB profit and pay 100,000 in tax (20% x 50%). Actual profit comes in at 2 million. You underestimated by 100%, way past the 25% threshold. The surcharge is 20% of the underpaid tax (100,000 THB), costing you an extra 20,000 that was completely avoidable.
Can You Overestimate Instead?
Yes, and there’s no penalty for it. The worst case is you pay more tax upfront and get credited at year-end. Some companies deliberately overestimate to avoid the surcharge risk.
The downside: that money sits with the Revenue Department earning you nothing for 6+ months. We aim for accuracy: close enough to avoid the surcharge without tying up unnecessary cash.
How We Handle It
We base your estimate on actual first-half financials, not guesswork. We look at your revenue trend, expenses, seasonal patterns, and any one-time items to project a realistic full-year number.
First-year companies are exempt from PND.51 filing. After that, it’s mandatory every year even if you expect a loss, though a loss estimate means zero tax payment.
Related Tax Guides
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Katwalee Matar (Lee)
Co-Founder & Managing Partner
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