Tax invoice defects that block input VAT credit in Thailand

01Why this is the first gate

When an exporter applies for a refund of accumulated input VAT, the reviewer is looking at a body of evidence: every input amount you claim has to be supported by a compliant tax invoice. If an invoice does not hold up, that line is struck out. Strike out enough lines and you lose refund value — and you invite a closer look at the quality of the books as a whole. See how the export VAT refund itself works.

The particular thing about invoice problems is that they happen at the moment the invoice is accepted, and the window to fix them is short. An invoice from three years ago made out in the wrong name is hard to have reissued today: the supplier may have been dissolved, the person who handled it may have left, or they may simply decline. So the right approach is checking day to day, not a scramble before you file.

02Four things to check on every invoice

Four checks, on each invoice, as it comes in.

• All particulars present. The issuer's name and tax ID, the buyer's name and tax ID, a description of the goods or services, the amount and the tax shown separately, the issue date and the invoice number. These are the basic elements of a valid tax invoice, and missing any one of them risks the line being struck out.
• The buyer matches the entity. The invoice has to be made out in the applicant company's legal name and tax ID. Made out to an affiliated company, made out to an individual, or using a short form or a former name — all frequent problems.
• The period is right. The date on the invoice has to line up with the period it is booked in and with the tax month it is reported in. Booking across periods, or reporting in the wrong month, surfaces when the numbers are cross-checked.
• It corresponds to a real transaction. It can be traced back to a purchase contract, a goods receipt and a payment record. Invoice without goods, and goods without invoice, are both hard defects.

One more category is easy to overlook: photocopies, illegible print, invoices with alterations on them. A defect in form can equally lead to a line being struck out on review — and raised at the moment the invoice arrives, the supplier reissues it and the problem is gone.

03Not all input VAT is creditable

Even where the invoice itself is compliant, there is a class of expenditure whose input VAT the tax law does not allow to be credited — spending unrelated to the business, certain categories of cost, and so on. Mixed in with creditable input VAT and reported as such, it is struck out the same way.

What we suggest in practice: separate non-creditable input VAT in the chart of accounts, sorting it as the invoice is booked rather than filtering at filing time. This is the same idea as keeping a separate sub-ledger for non-deductible items in the annual corporate income tax return — move the judgement forward to the moment the item arises, and every step after it gets easier.

04Who should be doing the checking

The usual gap in responsibility looks like this: purchasing only cares about obtaining an invoice, accounting only cares about booking it, and nobody is responsible for judging whether that invoice will stand up in a refund review. The result is that the invoices get their first systematic check three years later, when the refund is applied for, by which point the problems can no longer be fixed.

The workable answer is to give whoever receives invoices a checklist — the four checks above — and have them run through it on the spot, returning anything that fails for reissue. It takes under a minute per invoice, and it decides whether that refund comes through cleanly years later.

05If your historical invoices already have problems

Sort first, then deal with them. Particulars missing where the supplier can still reissue is usually fixable; the wrong buyer entity and the wrong period each take a different route; where the supplier has been dissolved or will not cooperate, those items have to be assessed on their own. List the items that will not tie out by category, and work through them category by category rather than as one pile.

What share of your existing invoices is compliant, which periods the problems cluster in, and how much is fixable against how much is not, all have to be verified invoice by invoice against the input VAT ledger and the physical invoices. Before deciding whether to apply for a refund at all, do a self-check first: problems you find yourself can be handled in your own time, while problems the reviewer finds mean a cycle of supplementary filings. What the export VAT refund engagement covers.