Input VAT in Thailand: How to Protect Your Tax Credits from Rejection

How Input VAT in Thailand Actually Works

Thailand operates a standard value added tax system under the Revenue Code, administered by the Revenue Department. VAT-registered operators charge 7% output VAT on their sales and pay 7% input VAT on their purchases. Each month, they file Form PP.30 and remit only the difference. When input VAT exceeds output VAT, the business either carries the credit forward or claims a refund. For newly established companies, sound VAT handling should form part of the wider accounting and tax compliance framework from day one.

The system depends on one document above all others: the full tax invoice. Under Section 86/4 of the Revenue Code, only a valid full tax invoice entitles a buyer to claim an input VAT credit. Consequently, the tax invoice is not mere paperwork. It is the legal key that unlocks the credit, and its validity depends on facts that the buyer often cannot see.

Why Good-Faith Buyers Still Lose the Credit

The most damaging disputes arise under Section 82/5(2) of the Revenue Code, which blocks any input tax claimed from a tax invoice issued by a person not lawfully entitled to issue one. In practice, two situations trigger this rule.

First, the supplier may never have genuinely made the sale. The invoice describes goods or services that were never actually delivered, so the tax authority treats the document as a “sham” invoice. Second, the supplier may have issued a real invoice, collected the 7%, and then vanished without remitting the tax to the state. In both cases, the Revenue Department can reject the buyer’s input VAT, even though the buyer paid in good faith.

Crucially, checking the supplier’s VAT registration number on the Revenue Department website offers no legal safe harbor. Registration confirms that a business is enrolled in the VAT system; it does not guarantee that a particular transaction was genuine or that the seller will remit the tax. Therefore, a valid registration cannot, by itself, save your credit.

The Burden of Proof Falls on the Buyer

Here lies the point that surprises most international businesses. When the Revenue Department challenges an input VAT claim, the taxpayer, not the department, must prove that the transaction was real. Recent Supreme Court (Tax Division) decisions have reinforced this position, confirming that the buyer bears the burden of showing that the supplier genuinely sold the goods, delivered them, and received payment.

As a result, the practical question is rarely “Did I act honestly?” Instead, it is “Can I prove, years later, that this purchase truly happened?” A company that cannot reconstruct the transaction with documents will usually lose, regardless of its intentions.

This burden weighs most heavily on digital and cross-border commerce. When buyers and sellers never meet, when orders arrive through a platform, and when goods ship directly from a third party, the evidence trail is thin. The same challenge appears with imported goods, where customs duty and import VAT add further documentation demands. Ironically, the businesses driving Thailand’s digital economy face the greatest exposure precisely because their transactions leave the lightest paper trail.

What a Rejected Claim Actually Costs

A disallowed input VAT credit rarely arrives alone. Once an assessment official acts under Sections 88 and 88/1 of the Revenue Code, the bill typically combines three layers of liability.

Because assessments often land more than a year after the transaction, the surcharge alone can be substantial by the time the notice arrives. When these layers combine, the true cost of one bad supplier can dwarf the original purchase value.

Building a “Know Your Supplier” File

The most effective defense is preventive. Before and during each significant transaction, assemble evidence that a reasonable, arm’s-length purchase genuinely occurred. Think of it as due diligence for tax, not just for commerce. A strong file usually includes the following.

• Supplier verification: a screenshot of the VAT registration check, company affidavit, and evidence the business physically operates.
• Commercial trail: quotations, purchase orders, contracts, and email or chat correspondence that show negotiation.
• The tax invoice: a complete full tax invoice with every particular required by Section 86/4, matched to the goods or services received. Where available, an electronic tax invoice (e-Tax Invoice) issued through the Revenue Department system adds an extra layer of authenticity.
• Proof of payment: bank transfer records showing money moving to the supplier’s own account, not to an unrelated third party.
• Proof of delivery: shipping documents, goods-received notes, photographs, warehouse or inventory records, and, for services, deliverables.

Above all, keep these records together and retrievable. The Revenue Code generally requires businesses to retain documents for at least five years, and disputes frequently reach back that far. A file that is complete but scattered is almost as weak as no file at all.

If You Receive a VAT Assessment: Deadlines Matter

Should an assessment still arrive, the clock starts immediately, and the deadlines are strict. Missing them can extinguish your right to challenge the tax altogether.

First, you must file an administrative appeal using Form Por.5 with the Commission of Appeal within 30 days of receiving the assessment. If you miss this window, you generally lose the right to appeal and must pay the full tax, penalty, and surcharge.

Second, if the Commission of Appeal rejects your case, you may appeal to the Central Tax Court within 30 days of receiving that decision. From there, further appeals may proceed to the higher courts. Throughout, the quality of your contemporaneous documentation, gathered long before the dispute, largely determines the result.

A Commercial Strategy, Not Just a Compliance Task

For foreign investors, the lesson is strategic. Input VAT in Thailand should sit at the center of tax planning, alongside corporate structure and transfer pricing, rather than at the margins as a bookkeeping afterthought. Two habits make the difference.

First, integrate supplier due diligence into procurement. Onboarding a new vendor should trigger the same scrutiny you would apply to any counterparty, with tax evidence captured automatically, much as you would when setting up a company in Thailand and building its compliance foundations. Second, keep dispute readiness in mind from day one. Because the burden of proof rests on you, the file you build today is the case you will present years later. Companies that adopt this discipline convert a hidden liability into a managed, predictable risk.

Frequently Asked Questions

This article is provided for general information only and does not constitute legal or tax advice. VAT outcomes depend on the facts and evidence of each transaction and on current Revenue Department practice. Businesses should obtain professional advice before relying on any input VAT position or responding to an assessment.