For SME owners, startup founders and freelancers whose income has grown to the point of VAT registration, the first confusing question is usually "what is P.P.30?" Why does the accounting firm chase invoices at the end of every month — and if there was no revenue at all this month, does anything still need to be filed?
In this article SiamAccount breaks down how P.P.30 works, states the legal position clearly, and shows how to plan cash flow around it so you never pay a penalty.
What is P.P.30?
In short: P.P.30 is the monthly VAT return (7%) that every VAT-registered operator files to report output tax and input tax to the Revenue Department, establishing whether tax is payable that month or a refund is due.
From a management point of view, P.P.30 is more than a filing obligation — it is a read on the liquidity of the business. What matters is keeping the input and output tax reports in order so the two can be offset under the Revenue Department's formula.
Output tax
The 7% you add and collect from customers when you sell goods or services. This money is not your revenue — you are holding it on behalf of the state.
Input tax
The 7% you pay suppliers when buying materials or paying expenses. This can be offset against output tax, reducing what you owe.
How VAT is calculated on the P.P.30
In short: output tax minus input tax equals the amount payable, or refundable. If output tax is higher you pay the difference; if input tax is higher you can claim a cash refund or carry the credit forward to the next month.
Two scenarios for a typical SME:
| Item | Case 1: tax payable (output > input) | Case 2: refund due (input > output) |
|---|---|---|
| Net sales (before VAT) | THB 100,000 | THB 20,000 |
| Output tax (7%) | THB 7,000 | THB 1,400 |
| Net purchases (before VAT) | THB 50,000 (materials) | THB 200,000 (machinery) |
| Input tax (7%) | THB 3,500 | THB 14,000 |
| Result (output − input) | 7,000 − 3,500 = +THB 3,500 | 1,400 − 14,000 = −THB 12,600 |
Who has to file a P.P.30?
In short: any individual or juristic person registered for VAT. That means businesses with annual revenue above THB 1.8 million (mandatory registration), and businesses below that threshold that registered voluntarily.
Entering the VAT system is the first step in raising a business to a higher standard. If you want to trade with large organisations, being able to issue a tax invoice is a genuine commercial advantage.
⚠️ Critical: the zero return
Once you are VAT registered, then even in a month where the business earned nothing at all (zero sales) or has not started trading, you must still file a nil P.P.30 every month. Never assume no revenue means no filing — skipping it triggers a criminal fine immediately.
When is the P.P.30 due?
In short: the P.P.30 summarises the previous month and is filed in the current month. Paper filing is due by the 15th; filing online through e-Filing extends the deadline to the 23rd.
E-filing is the modern standard. Beyond adding eight days of runway to your cash flow, it materially reduces document errors.
Example: tax invoices dated 1–31 January must be summarised and filed on a P.P.30, with payment if due, by 23 February.
Document checklist before filing
In short: to let your accountant close the month on time, gather (1) the output tax report, (2) the input tax report and (3) complete original tax invoices — ready in the first week of the following month.
- ✓Collect all output tax invoices (copies) issued to customers that month, in number order.
- ✓Collect all input tax invoices (originals) received from suppliers — each must show your company name, address and tax ID correctly.
- !Separate ordinary cash receipts: a receipt that does not say "tax invoice", or is missing required details, cannot be claimed as input tax.
- ✓Enter the data into the accounting system, or send it to your accounting advisory team to review.
Penalties for filing late
In short: a late P.P.30 attracts three separate charges — a criminal fine (THB 300–500), a penalty of one to two times the tax due, and a surcharge of 1.5% per month.
The Revenue Department treats VAT strictly, because it is state money that you merely collect on its behalf. Mistakes escalate quickly:
1. Criminal fine
2. Penalty
3. Surcharge (interest)
(An auditor's tip: good corporate tax planning means having reminders and cloud-based document collection in place, so human error never causes a missed filing.)
Case study: rebuilding VAT for a Chiang Mai hotel
Success Story
A Chiang Mai hotel faced back-dated VAT penalties after recording input tax from OTA platforms incorrectly. We rebuilt the process and recovered over 30% of the cash flow at risk.
A hotel and accommodation client took most bookings through Booking.com, where commission handling makes the VAT treatment complex. Staff recorded input tax in the wrong periods, so the P.P.30 figures did not match reality and the business was flagged for review.
Our team cleaned up the backlog, reconciled every sales figure, and set up cloud accounting linked to the front desk — giving the owner a real-time VAT position and ending the exposure to retrospective penalties entirely.
Frequently asked questions about P.P.30
Q1: An input tax invoice arrived late. Can it be claimed in a later month?
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Yes. The law allows an input tax invoice to be claimed in a later month, but no more than six months after the month it was issued. For accurate cash flow, though, it is still best to record it in the period the transaction actually occurred.
Q2: We sell online to retail customers who never ask for a tax invoice. Do we still file?
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Yes. Once revenue exceeds THB 1.8 million and you are in the VAT system, you must issue an abbreviated tax invoice or record a daily sales summary, and remit the 7% output tax — whether or not customers ask.
Q3: Can fuel receipts be claimed as input tax?
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Only for pickups and trucks used for the business. Fuel for a passenger car cannot be claimed as input tax on the P.P.30 under any circumstances.
Q4: The original input tax invoice is lost. What now?
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Never file using a photocopy. Ask the supplier to issue a substitute tax invoice, stamped and signed, which can then serve as valid tax evidence.
Summary: managing P.P.30 so it never slows the business down
Filing a P.P.30 is not merely a legal duty — it is an index of your financial discipline. If the back office is disorganised, penalties quietly erode the EBITDA you worked to earn, and that damage shows up badly later when you need to prepare financials for a loan.
If you run a business in Chiang Mai, Lamphun or Lampang and you are looking for a specialist to take the tax system off your hands, we can help.
SiamAccount will build your tax structure properly
With our full corporate accounting service, tax stops being the thing that holds your growth back. Our CFO team handles the system end to end.