The shipments already cleared Customs years ago. Can they really be reassessed now?

Yes. Clearance is not a final determination. A post-clearance audit reviews entries that were already released, and duty can be reassessed on them. This is precisely why the exposure is usually much larger than importers expect — a single classification or valuation position applied consistently over a long period multiplies across every entry that used it. The look-back period is set by law and should be confirmed with counsel against your own entry dates, because it determines how many entries are genuinely in scope.

Should we just pay the assessment to make it go away?

Sometimes, but not before you understand what paying concedes. Settling one assessment on a classification or valuation position implicitly accepts that position, which can then be applied to every future shipment and can weaken your argument on entries still under review. Where the position is defensible, paying quickly can be the more expensive choice over a two-year horizon. The decision should be taken on the whole entry population, not on the letter in front of you.

Customs is asking about payments we made to the seller outside the invoice. Why does that matter?

Because customs value is not simply the invoice figure. Certain payments connected to the imported goods may have to be added to the declared value even though they were invoiced separately or paid to a different party — royalties and licence fees tied to the goods, tooling or materials supplied to the manufacturer, and certain freight and insurance elements depending on the delivery terms. These additions are the single most common finding in a valuation audit, and they are usually made in good faith by a finance team that never saw them as import costs.

We buy from our parent company. Does that change the analysis?

It changes the starting point. Where buyer and seller are related, the price may still be accepted, but you should expect to be asked to demonstrate that the relationship did not influence it. That is a documentation exercise — transfer-pricing material, comparable pricing, and the commercial logic of your margins — and it goes far better when it is prepared in advance rather than assembled under audit deadlines.

Can we correct an error ourselves before Customs finds it?

Voluntary correction exists and can improve your position materially, but it is not automatically the right move. It works best where the error is discrete, quantifiable and clearly historic. It works badly where the underlying position is arguable, because disclosure concedes the point across every entry. Take advice on the whole picture before disclosing anything — the sequence is difficult to reverse.

Who should handle this internally?

Appoint one owner, usually the finance director or the import compliance manager, and route everything through them. The most damaging audits we see are the ones where the customs broker, the warehouse and three people in finance each answered questions separately, producing inconsistent explanations that then had to be retracted. Your broker is a valuable source of records but should not be the sole voice responding on your behalf.

Thailand Customs Post-Clearance Audit: What a Foreign-Invested Importer Does in the First 30 Days

The letter has arrived

A post-clearance audit does not stop your containers. That is exactly why importers underestimate it.

The letter typically asks for entry documents, invoices, contracts and payment records covering a period that has already closed. Nothing at the port changes. Operations continue. And then an assessment arrives covering years of shipments, because a single position applied consistently multiplies across every entry that used it.

This guide is for the CFO, finance director or import compliance manager who has to decide what happens in the next month.

General information only, not advice on a specific matter. The audit look-back period, penalty exposure and deadlines are set by law and change over time — confirm the current position with counsel against your own entry dates.

1. What an audit is, and what it is not

Clearance is a release of goods, not a final ruling on duty. A post-clearance audit revisits entries already released and tests whether the duty paid was correct.

Two consequences follow, and importers routinely miss both:

The exposure is historic and cumulative. You are not arguing about one shipment.
It is a documents exercise, not a goods inspection. What decides the outcome is your file, not your product.

2. Why Customs picked you

The recurring triggers:

Declared value that sits below comparable imports of similar goods
Classification that attracts a lower rate than the authorities consider correct
Origin claims used to obtain preferential treatment under a trade agreement
Related-party pricing where you buy from a parent or affiliate
Privilege use — free-zone, bonded, BOI or duty-drawback entitlements
Sector sweeps, where an industry is reviewed and you are simply in it

Knowing which trigger applies changes what you prepare. Do not assume; establish it from the scope of the documents requested.

3. The first 30 days

Freeze the records. Entries, invoices, contracts, payment evidence, correspondence with the supplier and the broker, and the systems that generated them. Do not tidy anything.
Map the entry population. Which entries, which period, which product lines, which declared positions. You cannot assess exposure without knowing the denominator.
Appoint one internal owner and route all communication through them.
Reconstruct the decision. Who set the classification, on what basis, and was there advice or a ruling behind it? A documented, reasoned position — even if ultimately wrong — is treated very differently from one nobody can explain.
Take advice before answering substantive questions. Early written answers become the frame for everything afterwards.

4. How declared value is tested

The starting point is the price actually paid for the goods, but that price is subject to additions and conditions. The additions importers most often miss:

Frequently missed	Why it surfaces in an audit
Royalties and licence fees related to the goods	Paid by a different department, treated as an IP cost, never seen as an import cost
Assists — tooling, moulds, materials supplied to the manufacturer	Provided free or below cost, so they never appear on any invoice
Freight and insurance elements	Treated inconsistently across delivery terms
Commissions	Buying and selling commissions are treated differently
Post-importation payments and rebates	Credit notes and retrospective adjustments that alter the real price

Where the declared value is not accepted, alternative valuation methods are applied in a prescribed sequence. The practical point for a CFO: you are much better off explaining your own value than having one constructed for you.

5. Classification and origin

Classification disputes turn on the objective characteristics of the goods, not on what the product is called commercially or how your ERP labels it. Assemble the technical specifications, composition and function early, and be consistent — a description written for marketing that contradicts your declaration is a gift to the other side.

Origin claims under a trade agreement carry their own evidential burden. If you claimed preference, you need the supporting documentation to still exist, and it must match the goods actually shipped.

6. Once an assessment is issued

The sequence is: assessment → objection → appeal → Tax Court litigation. Each stage has its own deadline, and those deadlines are short and strictly applied.

The decision at each stage should be taken against three questions:

How strong is the technical position on the merits?
How many entries, past and future, does conceding it affect?
What continues to accrue while the dispute runs?

That last point matters. Interest and surcharge exposure generally continues to build during a dispute, so a weak case fought slowly is the worst of both worlds. Equally, a strong case conceded for speed sets a precedent your business then lives with on every future shipment.

7. Voluntary disclosure

Correcting an error before it is found can materially improve your position, but it is not a reflex.

It tends to help where the error is discrete, historic and quantifiable — a keying error, a missed addition on a specific contract, a privilege applied to goods that did not qualify.

It tends to hurt where the underlying position is arguable, because disclosure concedes it across every entry that used it, including entries not currently under review.

8. The evidence pack

What your lawyer needs on day one:

The audit notice and every communication received so far
A full entry listing for the period, with declared values and classifications
Supplier contracts, purchase orders and the invoices behind the entries
Proof of payment, including anything paid outside the invoice
Any royalty, licence, tooling or cost-sharing agreements with the supplier or an affiliate
Transfer-pricing documentation where you buy from a related party
Preferential origin documentation for any claim made
Correspondence with your customs broker
Any ruling, advice or precedent relied on when the position was set

Item 9 is the one that most often does not exist and most often would have helped.

9. Stopping recurrence

An audit that ends without changing anything upstream is an audit you will have again. What actually changes outcomes:

One owner for classification decisions, with the reasoning written down
A standing review of supplier payments that sit outside the invoice
Alignment between transfer pricing and customs value, which are frequently managed by different teams to different logic
A rule that new products get classified before the first shipment, not after
Retention of import records that outlasts the look-back period

Summary

Stage	The decision
Letter arrives	Freeze records, map the entry population, appoint one owner
Information requests	Take advice before substantive written answers
Assessment issued	Judge on the whole entry population, not on this letter
Objection and appeal	Weigh the merits against what accrues during the dispute
Afterwards	Fix the upstream process, or expect the same audit again

The cost of an audit is set less by the original error than by how the first month is handled.

Our tax and customs team acts for foreign-invested manufacturers, importers and distributors. Initial consultation is free — call +66 92 254 2045 or send us the details. See also tax and customs services and our factory and industrial estate guide.

This guide is published by Suwanvara Law Firm — a Khon Kaen law firm established in 1986. General information only, not legal advice on a specific matter.