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HTS Statistical Suffixes: What the Last Digits of a 10-Digit Code Actually Do

Updated October 2026. Every figure below is recomputed from our structured extract of the US Harmonized Tariff Schedule; sources are cited inline.

A supplier sends over a classification: 6110.90.90.15. Your spreadsheet has been using 6110.90.90. Same thing — right? The instinct says the extra digits are bureaucratic noise, and most of the time the instinct is half-right: the duty will not change. But those trailing digits decide whether your knitwear enters under the correct fiber-restraint program, whether a trade action's language reaches your shipment, and occasionally whether CBP accepts the entry summary at all. This article counts every statistical suffix in the schedule, shows where they cluster, and draws the line between the digits that price your cargo and the digits that merely describe it. ^*

1. Ten digits, three jobs

The ten-digit HTS code stacks three layers of meaning:

Where does the 10-digit HTS break down from the 6-digit HS?

Digits one through six are the international HS stem; seven and eight are the US legal subheading carrying the rate; nine and ten are purely statistical. The split matters in practice because tools and quotes that stop at eight digits look rate-complete yet cannot reproduce the joins trade actions perform on ten-digit detail.

Do suffixes matter when the duty rate is identical?

Yes - three concrete ways: entry accuracy law, quota administration, and trade-action scope. CBP can pursue penalties under 19 U.S.C. 1592 for wrong statistics even at zero revenue impact, restraint programs fill by suffix bucket, and Chapter 99 measures cite ten-digit enumerations that decide inclusion.

• Digits 1–6 (the HS subheading) — internationally standardized product identity, negotiated through the World Customs Organization so that a code means the same thing in Hamburg and Los Angeles.
• Digits 7–8 (the legal subheading) — where US statutory rates live. Read the general column against these eight digits and you know the duty owed.
• Digits 9–10 (statistical suffixes) — US-only reporting subdivisions. They exist to feed trade statistics, administer quota and restraint programs, and let agencies track medically or politically sensitive goods.

The arithmetic behind that structure, computed fresh from the October 2026 schedule: 23,193 ten-digit lines rest on 11,414 distinct eight-digit codes — 2.03 statistical suffixes per code on average. Roughly a third of the schedule's length is description, not law.^*

2. How deep does the splitting go?

Suffix depth follows a steep power law. Most eight-digit families never split at all; a handful split into dozens:

Two details reward attention. First, no family splits into exactly two suffixes — when the schedule bothers to subdivide, it commits: the count jumps straight from one to three or more. Second, the 160 deepest families (ten-plus suffixes) cover 2,229 lines, close to a tenth of the entire schedule, so a small share of headings produces most of the classification surface area.

3. The extremes: 75 suffixes on one medicine line

The deepest family in the schedule is pharmaceutical: HTS 3004.90.92 carries 75 statistical suffixes, one for each tracked active ingredient — acyclovir, oseltamivir, valganciclovir, peramivir and their salts among them. Every one of the 75 shares the same general rate: Free. The depth exists because health authorities want import statistics at the molecule level, not because the customs value changes. ^*

Apparel takes the second model: suffixes as restraint-group tags. Line 6104.29.20 splits into 41 statistical suffixes whose descriptions read “Subject to cotton restraints (335)”, “Subject to wool restraints (435)”, “Subject to man-made fiber restraints (635)” and so on; 6204.29.40 mirrors it with 33. Here the suffix does bind commercially — not through the duty rate, but through which textile-program bucket your shipment reports into. 172 rows across the schedule carry such restraint-group language. ^*

4. The rule the data confirms: suffixes never reprice

We tested the folklore claim directly. For each of the 11,414 eight-digit families, we compared the general strings of all member suffixes:

• Families where suffixes differ on the general rate: 0.
• Families where suffixes differ on the special (preferential) column: also 0.

That is the cleanest invariance in the whole schedule, and it makes practical sense: the legal rate text attaches at the eight-digit subheading, while suffixes exist purely to disaggregate reporting. The corollary matters just as much — between eight-digit lines, rates can differ wildly, which is why our analysis of same-heading different-rate traps finds 1,011 six-digit subheadings carrying multiple rates one level up. Digits nine and ten describe; digits seven and eight price.

5. Why the suffix still matters at entry

1. Entry accuracy is legally required regardless of revenue impact. Wrong-statistics entries expose importers to penalty proceedings under 19 U.S.C. 1592 even when the duty outcome would be identical — negligence suffices, intent is not required.
2. Quota and restraint enforcement runs on suffixes. The apparel examples above are live program buckets; entering under the wrong fiber-restraint suffix can leave your cargo waiting outside a filled quota.
3. Trade actions cite ten-digit detail. Chapter 99 measures frequently enumerate statistical reporting numbers; the suffix decides inclusion. When it does, the amounts dwarf base rates — see our chapter-level trade remedy map for how that layer distributes.
4. Landed-cost models need the full code anyway. If your pricing engine stops at eight digits, it cannot reproduce the joins that trade actions and restraint programs perform; our guide to duty-rate types shows how the columns fit together.

For a worked path from product description to a defensible ten-digit code, start with how to find the right HS code; the free tariff calculator resolves any line against the current schedule.

Frequently asked questions

What are the last two digits of an HTS code for?

They are statistical suffixes: reporting subdivisions the US adds beneath the legal eight-digit rate line so that government agencies can track specific products. In the October 2026 schedule, 23,193 ten-digit lines hang off only 11,414 eight-digit codes - an average of 2.03 suffixes per code - and within every single eight-digit family all suffixes share one general duty rate.^*

Do statistical suffixes ever change the duty rate?

No. Across all 11,414 eight-digit families in the October 2026 export we found zero cases where suffixes under the same eight-digit code differ on the general rate - and zero cases where they differ on the special preferential column either. The suffix tells CBP what you imported; the eight-digit parent decides what you pay.^*

Why do some HTS codes have dozens of statistical suffixes?

Because some product categories carry heavy reporting or policy interest. The record holder is medicines: HTS 3004.90.92 packs 75 statistical suffixes tracking which active ingredient each preparation contains. Apparel lines split by fiber-restraint group instead - 41 suffixes on 6104.29.20 and 33 on 6204.29.40 - because textile trade limits are administered per fiber category such as cotton or wool restraints.^*

How many HTS lines have no statistical suffixes at all?

Most of them. 8,147 of the 11,414 eight-digit families - 71.4% - consist of exactly one ten-digit line with no further subdivision. Deeply split families are rare: only 160 families carry ten or more suffixes, yet those few account for 2,229 ten-digit lines, nearly a tenth of the whole schedule.^*

Can picking the wrong statistical suffix cause problems if the duty is identical?

Yes, three ways. CBP can require re-filing with penalty exposure under 19 U.S.C. 1592 even when revenue is unaffected; quota and restraint programs are enforced at suffix level, so apparel entered under the wrong fiber-restraint suffix can be denied entry; and trade-action coverage often cites ten-digit detail, so the suffix determines whether a Chapter 99 measure reaches you. Classification disputes on suffix choices are documented in CBP's public CROSS ruling database.

Where does the 10-digit HTS break down from the 6-digit HS?

At the US border of the harmonized system: the first six digits stay internationally standardized, digits seven and eight form the legal US subheading that carries the rate, and only the final two digits are national statistical suffixes. That is why a six-digit search returns dozens of lines - the schedule splits each HS stem into US-specific subheadings and then again into suffixes, 23,193 ten-digit lines hanging off just 11,414 eight-digit parents in the October 2026 export.^*

How do trade actions use the statistical suffix detail?

Chapter 99 measures and quota restraints frequently enumerate ten-digit reporting numbers, so the suffix - not the eight-digit parent - decides whether your product is inside a measure's scope. Apparel restraint programs are administered per fiber-category suffix, and penalty exposure under 19 U.S.C. 1592 attaches even when the wrong suffix would have owed identical duty. Filing the full ten digits accurately is therefore compliance-critical, not bookkeeping hygiene.

Sources and methodology

Dataset: data/hts.json, our structured extract of the US Harmonized Tariff Schedule (23,193 ten-digit rows, USITC REST export dated 2026-10-09T17:43Z, generated from hts.usitc.gov). Suffix counting strips dots from each ten-digit code and groups by the first eight digits; the rate-invariance test compares raw general and special strings within each family. Penalty authority referenced above is 19 U.S.C. 1592 (statute text); statistical-suffix definitions follow the USITC tariff FAQ; classification outcomes on suffix choices are searchable in CBP CROSS. Nothing in this article relies on projected or unpublished datasets.