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Same Fish, Five Tariff Lives: The Fresh-to-Canned Duty Ladder Across HTS Chapters 3 and 16

Updated 2026-11-07. Every figure below is recomputed at build time from the official USITC HTS export (vintage 2026-11-06T00:27:04Z); the headline line was also confirmed against hts.usitc.gov's public REST endpoint on the record date.

1. Why the ladder is a money question

Seafood is the clearest illustration in the entire tariff schedule of a principle most importers learn late: the HTS does not tax products, it taxes product states. A yellowfin tuna swimming, chilled, frozen, filleted or sealed in an airtight tin is chemically the same fish, but it wears five different tariff identities, and those identities differ by tens of percentage points of duty. Nobody argues about 301 tariffs here; the base schedule alone spreads the fish across the widest gap in the food chapters.

Sellers encounter this at the worst possible moment: after the buyer has agreed to a landed price. A Vietnamese or Ecuadorian processor quoting “frozen tuna loin” and “tuna loins packed in oil for retail” is selling into two different fiscal universes, and the difference is decided by wording that fits in one sentence of the tariff description. This page measures that sentence's consequences across the whole schedule — every heading a fish seller touches between the dock and the shelf.

2. The ladder census: nine headings, 770 lines

We grouped the schedule by four-digit heading and counted three things per band: total ten-digit lines, how many are Free in the general column, and how many carry a parseable ad-valorem percentage at all (with the median and maximum among those). The ladder runs from living fish to canned preparations:

Counts recomputed from data/hts.json (USITC export vintage 2026-11-06T00:27:04Z). “Ad-valorem lines” = lines whose general rate begins with a percentage; remaining non-Free lines carry specific-duty or compound rate strings and are excluded from the percentage statistics above.

Scan down the census and the industrial logic of the schedule appears. Live fish (0301): every single line Free — 16 of 16. Whole fresh or frozen fish: around 85 percent of lines Free. Fillets: 177 of 187 Free (94.7%), with a ceiling of just 6% on the handful of paying lines. Then the Chapter 16 cliff: prepared fish (1604) keeps only 36% of its 77 lines duty-free, it carries more ad-valorem lines than every Chapter 03 band combined (48 vs 41), and its maximum — 35% — sits on the exact product (tuna in oil) that dominates shelf-stable seafood retail. Prepared crustaceans (1605) soften back toward free because much of that trade enters under preference programs, though its paying lines still run to 10%.

If you have read our fabric-to-apparel tariff ladder, the shape is familiar: the schedule taxes transformation. Textiles start cheap as fabric and climb as garments; seafood starts free as a commodity and climbs exactly when someone adds the labor that consumers pay for. The policy goal is protection of domestic processing, and it works — which is precisely why exporters must plan around it rather than discover it.

3. Where the rates actually hide (and small-sample honesty)

A caveat that most census-style articles bury and we will not: in several Chapter 03 bands the ad-valorem sample is tiny. Frozen whole fish (0303) contains exactly 1 parseable percentage line — sturgeon roe at 15% — so its “median” and “maximum” are the same number by construction. Molluscs (0307) and crustaceans (0306) are nearly as thin (1 and 3 percentage lines respectively). The economically meaningful rate density of this ladder concentrates in one place: 1604, prepared fish, with 48 ad-valorem lines.

Within 1604 the paying lines cluster exactly where a merchandiser would expect: premium presentations. The 35% peak is 1604.14.10, tuna in oil; smoked, seasoned and otherwise dressed packs fill the mid-single to low-double digits. For the single-heading anatomy of that family — how the packaging wording splits the lines — see our deep dive on canned tuna duty in 1604.14. And because several headings contain both Free and paying lines under neighboring suffixes, review why one HS code can carry several rates before trusting a six-digit quote.

4. One tuna, three entries: a worked comparison

The ladder is abstract until you price it. These are actual current-schedule lines for the same species chain (recomputed from the same dataset as everything else on this page; the 35% was additionally verified the day of publication against the official USITC endpoint):

Rates shown verbatim from the schedule strings. Special-column codes are the preference programs under which the line enters Free.

Three practical readings of that table. First, the general-rate spread between the frozen whole fish and the oil-packed retail pack is the difference between quoting a competitive CIF price and losing the shelf. Second, the special column changes the game: 17 preference programs ride on 1604.14.10 at Free, so origin engineering (where the packing happens) matters as much as the classification itself — run the specific origin through our FTA eligibility checker before conceding the 35%. Third, whatever your lane, model the full stack including any trade-action exposure with the landed-cost duty calculator; the MFN rate is the floor of the conversation, not its end.

5. Playbook: choosing the honest line

1. Map your product's true state at import. Raw, filleted, cooked, in marinade, in airtight tin: each adjective points to a specific heading. Write the state down before touching a rate table.
2. Respect the Chapter 3/16 boundary. If the goods are prepared or put up for retail, Chapter 16 claims them regardless of how “fishy” they remain. Do not shop for the Chapter 3 rate unless the facts support it — misclassification to reach a Free line is a classic audit trigger, and penalties compound at liquidation.
3. Check the suffix, not just the heading. Rate dispersion inside families is documented in our sibling censuses; a six-digit answer is not a quotation-ready answer.
4. Price the preference column early. With 17 programs granting Free on the flagship line, rules-of-origin planning belongs in the commercial decision, not the compliance appendix.
5. Re-check at every schedule refresh. Lines move; our build-time drift gate exists precisely because last quarter's census is not this quarter's fact.

6. Frequently asked questions

1. Why does processing level change the duty rate at all?

Because the HTS taxes product states, not ingredients. Chapter 03 covers fish as a commodity (live, whole, filleted) and Congress has largely kept those lines duty-free or near-free, while Chapter 16 covers fish that has been prepared or preserved for the consumer — packed in oil, in airtight cans, seasoned. The processor's margin, not the fish, is what the higher lines tax. Our census of 770 lines shows the pattern: 565 of 619 Chapter 03 lines (91.3%) are Free, but barely half of the prepared-fish lines are.

2. What is the difference between Chapter 3 and Chapter 16 for fish?

Chapter 3 is fish as caught and minimally handled: live, fresh or chilled, frozen, filleted, dried, smoked. Chapter 16 is preparations: fish that has been cooked, canned, packed in oil or otherwise put up for consumption, including products where fish is the defining ingredient. The boundary turns on processing and presentation, which is why the same tuna can sit in 0303 as a frozen whole round or in 1604.14 as an oil-packed pack.

3. Is frozen fish duty-free into the US?

Mostly, yes. In our snapshot 85 of the 98 frozen-whole lines (0303) are Free, and 177 of 187 fillet lines (0304) are Free. But free is not the whole story: a few premium lines carry real rates — sturgeon roe in 0303 pays 15% — and the moment the same fish is prepared, the free density collapses: only 28 of 77 prepared-fish lines (1604) are Free, with a 35% peak on oil-packed tuna.

4. Can I classify my product in Chapter 3 to get the lower rate?

Only if the product genuinely sits there under the General Rules of Interpretation. Cooking, packing in oil or sealing in airtight containers generally pushes a fish product into Chapter 16 even if it looks like the same fish. Customs assigns the code by the condition of the goods at import, and misclassification to reach a Free line is exactly the pattern entry audits look for. When in doubt, request a binding ruling before you ship.

5. The general rate is 35% — can I still pay zero?

Often, yes. The 35% peak line, 1604.14.10 (tuna in oil), carries a Free special rate for 17 preference programs (A+, AU, BH, CL, CO, D, IL, JO, KR, MA, OM, P, PA, PE, R, S, SG in the current schedule). If your product originates in a partner country and meets the rule of origin, the preferential column applies. Check eligibility with our FTA eligibility checker and confirm the current column before quoting.

6. How was this article's data produced?

Every figure is recomputed at build time from our local copy of the official USITC Harmonized Tariff Schedule export (vintage 2026-11-06T00:27:04Z, 23,193 ten-digit lines). Band assignment uses the four-digit heading prefix; Free means the general rate string starts with “Free”; medians and maxima are computed only over lines whose general rate begins with a percentage, and we disclose how few such lines exist per band. The headline 35% on 1604.14.10 was additionally confirmed against hts.usitc.gov's public REST endpoint on the record date.

7. Recap

• The fish ladder spans 770 lines: 565/619 (91.3%) of Chapter 03 are Free; prepared fish/crustaceans drop to 82/151 (54.3%).
• Fillets are 95% Free with a 6% ceiling; the ladder's economic rates concentrate in 1604 (48 ad-valorem lines, median 6.0%, peak 35%).
• The flagship pain line is 1604.14.10, tuna in oil: 35% general, Free under 17 preference programs.
• Small-sample honesty: 0303's rate statistics rest on a single percentage line (sturgeon roe) — treat Chapter 03 medians as sparse-data artifacts, not market prices.
• Classify by the product's imported state, verify the suffix, then work the preference column; use the calculator to stress-test the full stacked cost before you quote.