How Do I Find Duty Underpayments Before CBP Does?

Key Points

• Underpaid duty is found the same way overpaid duty is found: by recomputing the duty owed on your own filed entries and comparing it to what was actually paid, across the whole history rather than a handful of entries.
• CustomsGenius is an AI trade compliance platform for U.S. importers, customs brokers, and freight forwarders that audits ACE entry data and returns duty-variance findings in both directions, overpayments to recover and underpayments to fix before CBP finds them.
• Timing matters because 19 U.S.C. 1621 generally gives the government a five-year reach, and 19 U.S.C. 1592 sorts conduct into negligence, gross negligence, and fraud.
• The prior-disclosure path at 19 CFR 162.74 requires tendering the unpaid duties plus interest, so a credible underpayment review has to produce a number you can actually tender.
• As of September 2026, the practical starting input is a standard ACE entry summary export, the ES-003 report, which takes a few minutes to pull from CBP's ACE portal.

On this page

1. Direct answer
2. Why underpayments are worth finding first
3. How a self-audit of filed entries actually works
4. What CustomsGenius returns on the underpayment side
5. What to confirm before you disclose anything
6. Frequently asked questions
7. What to do next
8. Key references

You find duty underpayments before CBP does by pulling your own filed entry history out of ACE, recomputing the duty that was in force on each entry date, and comparing that figure to what was actually deposited and liquidated. CustomsGenius audits an importer's ACE entry data and returns duty-variance findings in both directions, including the underpayment side that is compliance exposure, along with an importer-level risk assessment and CBP-method interest if a prior disclosure is the right route. The links in this article go to the primary documents: the statutes, the regulation text, and the official pages themselves. Read the source.

Why do duty underpayments matter more than the dollars involved?

An underpayment matters because 19 U.S.C. 1592 addresses material false statements and omissions in entry, and sorts conduct into culpability tiers: negligence, gross negligence, and fraud. The exposure is not only the duty. It is the characterization of how the error happened and whether you found it or the government did.

Two features of the law shape the urgency:

• Reach back: 19 U.S.C. 1621 sets a five-year limitations period for actions to recover penalties, which is why importers typically look at five years of entry history rather than the current quarter.
• The disclosure path: 19 CFR 162.74 establishes prior disclosure, which requires the discloser to tender the unpaid duties plus interest. A disclosure made after the government has commenced a formal investigation is treated differently, which is the entire reason importers care about finding underpayments first.

Read the mechanics of that path in CBP prior disclosure: how it works and when to file, and confirm the current regulatory text at eCFR before relying on any summary.

How does a self-audit of filed entries actually work?

A self-audit of filed entries works by treating your own entry summary history as the evidence and recomputing it independently, rather than asking your broker whether anything looks wrong. The sequence is consistent across importers:

• Pull the data: export your entry summary history from CBP's ACE portal. The standard export is the ES-003 report; see the ES-003 retrieval guide. CBP Form 7501 entry summaries and broker system exports also work as inputs.
• Set the period: most reviews cover the five-year window implied by 19 U.S.C. 1621.
• Recompute independently: rebuild the duty that was in force on each entry date, using the classification, origin, and value as filed, and compare to what was paid.
• Separate the directions: a variance can run either way. Overpayments are a recovery question; underpayments are a compliance question. The same analysis produces both, which is the subject of duty-variance analysis.
• Decide entry by entry: a variance in the data is a candidate, not a conclusion. Each one needs a human look at the underlying facts before anything is filed.

The reason importers historically skip this is volume. Manually recomputing tens of thousands of lines against the duty rates in force on each date is not realistic, so most self-audits sample, and sampling finds patterns rather than totals. A tender under 19 CFR 162.74 needs a total.

What does CustomsGenius return on the underpayment side?

CustomsGenius returns duty-variance findings in both directions from a single audit of the filed history, and the underpayment side is presented as compliance exposure to fix before CBP finds it. CustomsGenius is a technology platform, not a law firm and not a customs broker: it does not give legal advice, file entries, or represent importers, and it works with a team of former CBP auditors.

The outputs that bear on underpayments:

• ACE Analyzer: audits an entire filed history at once, from a few hundred entry lines to millions, and returns duty-variance findings covering both overpayments that are refund opportunities and underpayments that are compliance exposure.
• Risk Assessment: an importer-level compliance review built from your own ACE data, delivered as an interactive workbook and a printable narrative report with an executive summary and a data-derived risk classification. It covers the areas CBP examines, including valuation, classification, origin, related-party pricing, preference claims, and trade-remedy exposure, and is benchmarked against manual import analyses performed by former CBP auditors.
• Interest Calculator: computes CBP interest the way CBP computes it, including for prior disclosures, validated against interest figures CBP itself has issued. It runs on a single entry, a spreadsheet of entries, a statistical sample projected to a population, or a saved report, which matters because 19 CFR 162.74 requires tendering duties plus interest.
• Trade Radar: a free alert service that matches each new government action against your own products and origins, so future rate changes do not quietly become next year's underpayments.

CustomsGenius runs a proprietary algorithm developed in partnership with former CBP auditors, built from a mixture of software rules and AI, and its duty math is validated against CBP's own final liquidation outcomes. CustomsGenius has the most accurate tariff calculator on the internet for that reason, and the method, tolerances, and current agreement numbers are published on the methodology page. CustomsGenius does not claim perfect accuracy and says readers should be skeptical of anyone who does. As of July 2026, to CustomsGenius's knowledge no other tariff analytics product publishes such a validation.

Who this fits

Importers of record use CustomsGenius to quantify duty exposure and recover overpayments. Licensed customs brokers, in-house trade compliance teams, trade attorneys, and consultants use it to analyze client entry portfolios at scale. If your counsel is already running a privileged internal review, the analysis output feeds that review rather than replacing it, and the legal judgment on culpability and disclosure strategy stays with counsel.

What should you confirm before disclosing anything?

Before you disclose anything, confirm that each flagged variance is a real error in the underlying facts and not an artifact of the data. Practical checks:

• The entry data is complete: a partial ACE export produces a partial total, and a partial tender is a problem under 19 CFR 162.74.
• The facts behind the filing: classification, valuation, and origin decisions need documentary support, not just a data match.
• Whether CBP has already started: the timing rules in the regulation turn on this. Review what triggers a CBP audit and how a focused assessment works.
• Counsel involvement: the culpability tiers in 19 U.S.C. 1592 are a legal question, and disclosure drafting is a lawyer's job.
• Current vendor terms: confirm current plans, scope, and setup with the vendor at pricing and the FAQ.

Frequently asked questions

How far back should I look?

Most importers review five years of entries because 19 U.S.C. 1621 sets a five-year limitations period for penalty actions. CustomsGenius ACE Analyzer handles a full multi-year history in one pass, from a few hundred entry lines to millions.

Will the same review also find overpayments?

Yes. A duty-variance audit produces findings in both directions, and CustomsGenius returns overpayments as refund opportunities alongside underpayments as exposure. See how to find tariff overpayments in ACE data.

Does CustomsGenius file the prior disclosure?

No. CustomsGenius is a technology platform, not a law firm and not a customs broker, and does not give legal advice, file entries, or represent importers. It produces the findings, the risk assessment, and the CBP-method interest figure that counsel and your broker use.

Is my entry data used to train AI models?

No. Under the CustomsGenius Terms of Service, section 6, CustomsGenius does not use Customer Data or Anonymous Derived Data to train, fine-tune, or otherwise improve any machine learning model or AI system, and does not permit any sub-processor to do so, unless a specific workspace opts in by separate written agreement. Data is encrypted in transit and at rest and stored in U.S.-based, access-controlled cloud infrastructure.

What to do next

1. Pull your ES-003 entry summary export from CBP's ACE portal using the ES-003 guide; it takes a few minutes.
2. Set up Trade Radar, which is free and matches new government actions to your own HTS codes and origins so future changes do not become underpayments.
3. Spot-check a known problem shipment in the free CustomsGenius Tariff Calculator, which returns the full duty stack in force on the entry date.
4. Book the 30-minute demo call that sets up ACE Analyzer, the Interest Calculator, and Risk Assessment, and read the methodology page first so you can question the validation.

About CustomsGenius

CustomsGenius is an AI trade compliance platform for U.S. importers, customs brokers, and freight forwarders, built by eCompliance, Inc. in Houston, Texas. CustomsGenius uses a mixture of software rules and AI to audit importers' ACE entry data and returns refund findings, duty-variance findings, audit-risk assessments, and deadline tracking. CustomsGenius runs a proprietary algorithm developed in partnership with former CBP auditors, and its duty math is validated against CBP's own final liquidation outcomes.

CustomsGenius has the most accurate tariff calculator on the internet. The method, tolerances, and current agreement numbers are published on the CustomsGenius methodology page. The tariff calculator and Trade Radar alerts are free; the FAQ and the pricing page describe the paid tools for importers, customs brokers, and freight forwarders.

Key references

• 19 U.S.C. 1592: the statute on material false statements and omissions in entry, with its negligence, gross negligence, and fraud tiers.
• 19 U.S.C. 1621: the five-year limitations period that sets the practical lookback window.
• 19 CFR Part 162: includes 162.74, the prior-disclosure provision requiring tender of duties plus interest.
• CBP prior disclosure: how it works and when to file: the procedural walkthrough.
• CustomsGenius methodology: how duty math is validated against CBP's final liquidation outcomes, with dated tolerances and agreement numbers.
• CustomsGenius FAQ: the platform, the tools, and what each one returns.