Every amount in a TariffTrust estimate comes from an official US source, through steps built to be checked. Here is what happens between an official text and a line of an estimate.
Official sources only
TariffTrust reads official US sources, and nothing else:
- the Harmonized Tariff Schedule, published by the US International Trade Commission (USITC), with the notes of its Chapter 99;
- the Federal Register, where proclamations, executive orders and agency notices are published;
- the presidential actions of the White House;
- the notices of the US Trade Representative (USTR);
- the CSMS messages of US Customs and Border Protection (CBP), and the notices and regulations behind the entry fees.
The sources are checked every six hours. Each document is archived with its fingerprint (SHA-256) when it is read, before anything is interpreted. A result says when the sources were last checked successfully and whether the checks work; the status page shows when each source was last read.
From legal text to rules
The base rates come straight from the tariff's own data. The additional duties of Chapter 99 are written for lawyers: which countries, which products, from which day, under which conditions, and how each combines with the others. TariffTrust turns each of them into a structured rule the calculator can apply:
Read by a specialized AI
An AI set up by TariffTrust for US tariff texts reads each change and writes the rule, citing the official passages behind each of its choices.
Checked against the official text
Automated controls hold every rule to the archived text and to the tariff itself before it can be used.
Reviewed by a person
Whatever is not clear-cut goes to human review, and the rules in service are checked again regularly.
A rule that does not pass is left out: the products it covers get no estimate rather than a wrong one.
Official notices, ahead of the tariff
A proclamation, a USTR notice or a customs message often changes duties days or weeks before the USITC writes the change into a new edition. A notice that changes duties is read and checked like an edition; until then, from the day it takes effect, the estimates of the goods it names are withheld. A duty that rests on such a notice is marked "ahead of the USITC tariff" in the estimate.
A calculation without AI
The amounts are calculated by a program from the rules in service: the same inputs and the same data always give the same result. A language model never computes an amount. A saved estimate keeps its data and engine versions, and replays to the cent without any online source or AI call.
Withheld, never guessed
When an amount cannot be established, because a Chapter 99 heading is not examined yet or is under review, a rate is under verification or a notice is not read yet, the amounts it may change are withheld and the estimate says why. An unknown amount is never shown as zero. The coverage page lists every Chapter 99 heading with its status.
Versioned, dated and sourced
The data in service is a publication: an immutable version of the tariff lines, the rules and the fees, drawn from one edition of the tariff, with the period it covers and the dates it was approved. It never changes; a change makes a new publication. Every estimate names its publication, and every line of an estimate links to its official source.
Corrections in the open
When a published rate turns out to be wrong, whether TariffTrust's own checks find it or a customer reports it, an incident opens: the estimates concerned are suspended, the workspaces whose saved estimates may be affected are told, and the status page shows it. The error is corrected and a new version published; a second notice then says which results were wrong and gives the corrected ones. Every correction is listed in the public changelog, and a correction of TariffTrust's reading is never presented as a decision of US Customs.
What it does not cover
An estimate is informational, not a customs determination. TariffTrust does not classify goods, and does not calculate antidumping or countervailing duties, nor taxes other than the entry fees. The limits of the service list everything outside its scope.
Updated October 29, 2026. General information as of that date, not legal or customs advice: the official texts prevail, and a licensed customs broker can confirm what applies to your goods.