How to Check If You Overpaid Tariffs: The Line-by-Line Method

Why "am I overpaying tariffs?" is now a checkable question

Customs duty overpayment used to be a niche audit topic. In 2026 it is a mainstream one, because the duty rules changed four times in twelve months: the Supreme Court struck the IEEPA tariffs on February 20, 2026, the Section 122 surcharge took effect at 10 percent on February 24, Section 232 was restructured on April 6, and restructured again on June 8. Every entry your broker filed was priced once, on the day it was filed, against whichever version of the rules was live that morning. Nothing re-prices it afterward unless someone goes back and checks.

This article is part of The Manufacturer's Guide to Checking Your Tariff Bill, which covers the whole recheck end to end. This piece covers the core method.

The documents you need and where to get them

Three document sets answer the question, and you already own all of them:

• Entry summaries (CBP Form 7501). The form your broker files with CBP for each import: the lines, values, codes, and duties for that entry. Your broker can send copies on request.
• Your ACE export. Any importer of record can open an ACE account with CBP and pull entry data as structured rows, including corrections filed after the original entry.
• Supplier invoices. They carry the product descriptions and values the duty math depends on, and they are how exclusion misses and value errors get caught. The entry alone cannot show either one.

The fast first pass: read the Chapter 99 codes

Before any deep checking, ten minutes with one 7501 tells you which programs you are paying. Each duty program shows up as a Chapter 99 code on the entry line: the 9903.88 range is Section 301, the 9903.01 range is the struck-down IEEPA programs, and the Section 232 and 122 programs carry their own ranges. The codes' presence tells you what was charged; their absence tells you what was never claimed, like an exclusion heading missing from a 301 line. The hard part is not reading the codes. It is knowing what the rates and rules behind them were on that entry date, which is the part that kept changing.

The seven error classes

Nearly every overpayment lands in one of seven classes. Check your lines against each:

Missed Section 301 exclusions. 178 exclusions run through November 10, 2026, written as prose product descriptions rather than codes. Lines whose invoice text matches exclusion language that was never claimed are refundable after the fact. Full guide: did your broker claim your exclusions?

The Section 122 surcharge stacked on 232 goods. Goods already subject to Section 232 do not pay the 10 percent surcharge. It gets charged anyway, because the non-stacking rule is obscure and nothing in the filing flow stops it.

Section 232 basis and tier errors. The 232 rules were rewritten on April 6 and June 8, 2026: full customs value replaced metal-content value and the rate tiers moved. Lines entered under the wrong basis or tier are pure re-math. Full guide: recheck every Section 232 line.

HTS misclassification.A code chosen years ago under one duty regime can be expensive under another. When a line's rate disagrees with how comparable goods enter, the difference is a review candidate for your broker.

Country-of-origin errors. Origin decides which programs apply at all. A supplier that moved production or an origin copied from an old setup puts the line under the wrong program entirely.

Missed USMCA qualification. Qualifying goods are exempt from the Section 122 surcharge. Canada and Mexico lines that qualified but entered without the claim paid a surcharge they did not owe.

Drawback never claimed. If you export, duties on Section 301 goods can be recovered up to five years back. The routing rules live in the refund pathways guide.

Rebuild one line by hand: a worked example

Take one line from an entry filed March 3, 2026: steel mounting brackets, entered value $30,000. The 7501 shows two charges on the line: the Section 232 duty, and the Section 122 surcharge at 10 percent, $3,000.

Now rebuild the line as of March 3. The brackets are 232-covered goods, and goods already subject to Section 232 do not pay the Section 122 surcharge. The 232 duty stands. The $3,000 surcharge should never have been charged. Paid: 232 duty plus $3,000. Owed: 232 duty. Finding: $3,000, on one line of one entry.

That is the entire method. Rate, value, program, date, compared against what was billed. The only hard part is knowing what the rules were on that date, which is exactly the part that changed four times in twelve months. The tariff check runs the same rebuild on every line you upload, priced against the rules in force on each entry date.

The deadline math

What is still recoverable is a function of dates, not of how good the finding is. Three windows matter, and you should verify each against your own entries with your broker, because liquidation dates vary entry by entry:

• Post Summary Correction: reaches back 300 days from the entry date, and no later than 15 days before scheduled liquidation.
• Protest (CBP Form 19): reaches back 180 days from the liquidation date. The deadline is absolute, with no extensions.
• Drawback: reaches back five years from import, on exported goods. Section 301 and Section 122 duties are eligible; Section 232 duties are not.

Entries liquidate continuously, so the set of entries you can still correct shrinks every week. That is not urgency theater; it is how the statute works. A finding you confirm in October may sit outside a window that was open in June.

What industry estimates claim, and what we can verify

Industry estimates put duty overpayments at 5 to 15 percent of duties paid. Treat those numbers as marketing from firms selling recovery services; they may be right, but you cannot check them. What we can verify first-party: in a recent run, Kynthar's duty engine priced $2.32 million of duty across 532 entry lines and reconciled the total to the dollar. The honest claim is not a percentage. It is that the math is checkable, line by line, against your own documents.

Check it by hand, or upload it

The manual method makes sense for a sample: pick your ten highest-duty entries, run the seven classes against each line, and hand the findings to your broker with the line references. It proves the method and usually settles whether a full recheck is worth it.

It stops scaling at the exclusion check and the effective-dated re-math: 178 prose product descriptions against every invoice line, and per-line rates that depend on the entry date, across thousands of lines. That is the part you upload. The full recheck method, including the duty stack and the do-it-yourself checklist, is in the pillar guide.

A useful rule for choosing: check by hand when the question is "is there anything here?" and upload when the question becomes "how much, on which lines, and by when?" The first question takes an afternoon and a sample. The second takes effective-dated rates applied per line across the whole entry history, plus a deadline computed per finding, and that is compute work, not judgment work. Whichever way you run it, the findings end in the same place: with your broker or counsel, as line-level evidence they can file from.