Monthly Tax Deadlines Every Thai Business Owner Must Know

Thai tax compliance runs on a monthly rhythm. Three authorities — the Revenue Department, the Social Security Office, and the DBD — each expect their own filings, on their own dates, in their own forms.

Missing one is rarely catastrophic the first time. Missing the same one twice is how a 1,000 baht surcharge snowballs into a 25,000 baht penalty plus interest. The cost of compliance is small. The cost of inattention compounds.

Below is the cadence we put on every client engagement. Dates are in calendar terms (e.g. "by the 7th") relative to the month after the activity occurred.

Surcharges in Thailand stack: a flat fine for late filing, plus monthly interest on the unpaid amount, plus — for VAT — an additional 1.5% per month uplift. A late PP.30 with 50,000 baht of VAT due can add 4,000–7,000 baht of penalty by the time the Revenue Department picks it up at audit.

Worse than the cash cost is the audit signal. Repeated late filings put your company in a higher-scrutiny bucket, and that scrutiny outlives the missed deadline by years.

Every PTNP engagement runs on a shared calendar. We send the document request at the start of the month, prepare and review by mid-month, and file before the deadline window closes — always with at least one day of buffer.

For business owners managing this themselves, the single most useful thing you can do is set three calendar reminders per month: one on the 5th (withholding), one on the 10th (social security), one on the 20th (VAT). Treat them as sacred.