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How to Audit Your Company's HTS Codes: A Six-Step Duty Review for Importers

Published 18 September 2026 · A process, not a product manual. Everything in steps 1 to 4 can be done with a spreadsheet and free public data.

Most importers have never reviewed their own tariff classifications. The codes were set once — often years ago, often by a broker, in a hurry, from a short product description — and they have been repeating on every entry since. The liability for them sits with the importer, not the broker, and in a period when the tariff schedule is being revised every few weeks, a code that was right in 2023 may be expensive now.

This is the review, in the order that finds the money fastest. The first pass is about half a day.

Why this sits with you. A customs broker acts as your agent. Using one does not transfer liability. The importer of record is required to exercise reasonable care in classifying its goods, and penalties for a material false statement or omission fall on the importer under 19 U.S.C. § 1592. A documented periodic review is also, in itself, evidence of reasonable care.

Step 1

Step two, without the spreadsheet. The rate-comparison step below is the slowest part of this review by hand. The free Duty Spread Checker does it per code in a second, and shows the fact that selects between the sibling lines.

Build the list

You need every HTS code your company imported under in the last twelve months, with annual customs value and duty paid against each. Three ways to get it:

One column people forget and then need: country of origin per line. Half of what follows depends on it.

Step 2

Rank by duty at risk, not by line count

Sort by annual customs value per code, and calculate duty paid per code. Do not sort by how often a code appears — a code used once on a $2m shipment matters more than one used 400 times on $5,000 shipments.

For most importers the top 20 codes are the great majority of the exposure. That is your review population. The long tail can wait for next year, and saying so explicitly is what makes this a half-day job rather than a project that never starts.

Step 3

Verify the base rate against the current schedule

For each code, confirm the column 1 general rate at hts.usitc.gov. It is free and authoritative.

Do not assume the rate you have on file is current. The schedule was revised seven times in the eight weeks to 9 September 2026. Note also whether the rate is a percentage or something else: rates written as 90¢/pr. + 37.5% or $1.646/kg cannot be applied without a quantity, and a system that quietly reads the percentage component alone will understate the duty on every unit.

Step 4

Read every sibling line under the same subheading

This is the step that most often finds money, and almost nobody does it.

Duty is set at the 8- or 10-digit line, not the 6-digit subheading. Read all the lines beneath your subheading and note the highest and lowest rate. In 61.4% of US subheadings with more than one rate-bearing line, those lines carry different rates — a median of 5 percentage points apart, and up to 40.5 at the extreme. Multiply the spread by your annual value on that code and you have the amount at stake in the classification being right.

Then ask whether you can actually prove which sibling applies. The discriminators are usually physical facts — material composition, value per unit, external surface area — that appear nowhere on a commercial invoice.

Full analysis of where the spreads are, by sector →

Step 5

Check the trade remedies, especially derivative Section 232

The base rate is rarely the whole duty. Confirm for each line which Chapter 99 measures attach:

MeasureLook forTypical rate
Section 232 — metalsSteel, aluminium, copper articles50% (UK 25%)
Section 232 — derivativesFinished goods containing those metals25%
Section 301 — ChinaLists 1–3, 4A by subheading25% / 7.5%
Section 301 — country-wide60 economies, from 24 July 202610% / 12.5%

The derivative row is the one that catches people. A household refrigerator has a base rate of Free and, from China, carries 25% Section 301 plus 25% Section 232 as a derivative article — 50% duty on a duty-free product. If you import appliances, machinery, furniture or fittings, assume Section 232 reaches you until you have checked.

Then check the escape that runs the other way: for articles outside chapters 72, 73, 74 and 76, if the applicable metal is under 15% of the article's weight, the Section 232 duty does not apply. You need evidence of the metal weight — a bill of materials or a supplier declaration, not an invoice.

How the measures stack, with worked examples →

Step 6

Separate refundable duties, then document everything

Split out any Chapter 99 lines in the 9903.01 or 9903.02 series. Those are IEEPA duties, they were held invalid from inception in February 2026, and CBP is refunding them against claims somebody files. Keep live Section 301 and Section 232 charges — including anything in 9903.05, which looks similar and is not refundable — out of any claim.

Which duties are refundable, and the look-alikes that are not →

Finally, write down the basis for every position you keep. For each reviewed code: why this line rather than its siblings, what evidence supports it, and who decided. That record is the difference between a defensible classification and an assertion, and it is what CBP's reasonable-care standard is asking for.

Where a line is genuinely uncertain and the amount is material, that is the moment to spend money: a licensed customs broker or customs attorney, and a binding ruling where the exposure justifies it. A ruling binds CBP and ends the argument prospectively.

What the first pass typically turns up

FindingDirectionWhat to do
Code sits on a wide-spread subheading with no evidence on fileEitherGather the discriminating fact; consider a ruling
Derivative Section 232 never applied to finished goodsUnderpaidCorrect promptly — this is the penalty-exposed direction
Section 232 applied where metal content is under 15%OverpaidDocument the weight and claim
Country-wide Section 301 charged on a line already paying 232OverpaidCheck note 52(f) exclusion
IEEPA duties paid in 2025–26RefundableClaim, oldest liquidation first
Base rate stale after a schedule revisionEitherRe-baseline and set a review cadence

A word about findings that go against you. A review that only looks for overpayments is not a review. If it turns up underpaid duty — and the derivative Section 232 row frequently does — that is the finding with a deadline and a penalty attached, and it is better found by you than by CBP. Prior disclosure exists for exactly this situation and substantially reduces exposure. Take that one to counsel before you take it anywhere else.

Where software helps, and where it does not

Steps 1, 2 and 6 are spreadsheet work and judgement; no tool removes them. Steps 3, 4 and 5 are mechanical lookups across hundreds of lines, which is where they stop being a half-day and start being a fortnight.

That is the part Vectelos automates. Give it a supplier quotation, proforma or commercial invoice — or a list of codes you already hold — and for each line it returns the base rate, the rate spread across the sibling lines it could not distinguish, every Chapter 99 measure with the statute and subdivision behind it, and the fees, as a worksheet you can hand to a broker. Where the schedule does not let it decide, it refuses rather than guessing: a rate it cannot compute without a unit of quantity is reported as not computed, never as zero.

Two things it will not do, stated plainly. It does not file anything — it is not a licensed customs broker, and the worksheet is an advisory estimate, not a CBP form. And it does not claim to classify goods automatically from a short description: published state of the art for that task remains well below what a person who knows the product achieves, ours included, which is why the tool offers candidate lines in plain language and asks the person who bought the goods to confirm. What is exact is the duty arithmetic underneath — all 13,801 published rates verified line-by-line against the USITC schedule, and re-verified on every revision.

Related guides

References

This article is general information about US customs procedure and the tariff schedule. It is not legal advice, not a customs ruling, and not a substitute for a licensed customs broker or customs attorney. Vectelos does not file entries, protests or disclosures. Classification and trade-remedy positions depend on facts specific to your goods, and the measures described here change frequently — the schedule was revised seven times in the eight weeks before publication. Figures are as published on 18 September 2026.