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China-origin laptops with a Free base rate now owe 12.5% under 2026 Section 301 tiers
InvoiceTariff's open ruleset charges China-origin laptops 12.5% under the 2026 global Section 301 program despite a Free base rate. Every layer of the stack changes on its own date, so landed-cost code with hardcoded rates falls behind.
The Engineer · Build desk
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What happened
- The post breaks a China-origin entry into the MFN base rate, Section 301 layers, Section 232 for covered metals, and user fees that often cost more than the duties.
- Added as the post stacks them, a cotton T-shirt pays 16.5% MFN, 7.5% under List 4A and the 12.5% China tier, for 36.5% before fees.
- The 10% IEEPA fentanyl tariff layer was struck down on 2026-02-24, the post says, and the engine now keeps it only as a historical layer.
- The MFN rows in ruleset v0.3.2 carry sample flags, and the post calls them estimates that are not customs-certified.
Compiled by The EngineerSomething wrong?How this is made
Why it matters
- decision Landed-cost tools now need rule tables keyed by effective date, or a new code release each time a tariff tier or a fiscal-year fee row changes.
- exposure Importers who paid the IEEPA layer may have refunds to recover, and any estimate that still adds the 10% overstates what a new China entry costs.
- constraint Until its MFN rows are verified, the engine produces planning estimates that cannot stand in for a customs-certified duty figure.
The part of the post worth copying is the data file. InvoiceTariff's engine reads one JSON ruleset, ruleset-seed.json v0.3.2, dated 2026-09-24, according to its maintainer [2]. Each layer is a separate table. The fee table is keyed by fiscal year, and its FY2027 row carries validFrom 2026-10-01 and validTo 2027-09-30 [5]. The global Section 301 table has its own start date, 2026-07-24 [3]. So a ruleset cut in September already holds the October fee row. Code that picks rows by entry date prices a September entry and an October entry differently from the same build.
Constants written into code go stale at each of those dates. A function holding FY2026 fee values has a $33.58 MPF floor [6], a dollar below the current $34.58 [19]. That bug costs a dollar. The global tier is the expensive one. A laptop under HTS 8471.30 has a Free MFN rate and sits on none of the 17 China list lines in the ruleset [7]. An engine that knows only MFN and the China lists returns zero duty for it. Add China's 12.5% tier and a $50,000 laptop entry owes $6,250 [15]. The post says "a lot of landed-cost spreadsheets don't know it exists yet" [20]. It does not say how many.
The post's case on fees is that they are not rounding errors and often cost more than the duties [1]. The FY2027 merchandise processing fee is 0.3464% of value, bounded by a $34.58 minimum and a $670.86 maximum [5]. Dividing through, the floor binds below about $9,983 of declared value [16] and the cap above about $193,666 [17]. The harbor maintenance fee adds 0.125%, on ocean shipments only [5]. Ship that $50,000 laptop entry by ocean and MPF is $173.20, HMF is $62.50, and duty plus fees comes to $6,485.70 [18]. The same table lists flat fees for informal entries: $2.69 up to $100 of value, $8.06 up to $1,000, and $12.09 up to $2,500 [10].
The runnable TypeScript in the post covers the main path only, with no exclusions, no Section 232 matching and no informal tiers [11]. The China table needs the same caution. It holds 17 list lines in this ruleset [7]. A code missing from 17 seed lines is absent from the seed. Whether it is on a USTR list is a separate lookup.
The provenance design is good work. Every row carries legalBasis and source fields [12]. China's row in the global table cites Trade Act 1974 Section 301 and FR 2026-15181 Section 1(a)(i), under what the ruleset calls a global forced-labor program, and it is one of 60 country tiers [3]. When a client asks where 12.5% came from, the row answers with a Federal Register citation [12]. The maintainer's rule is that the stack cannot be computed without a versioned dataset, "because every layer changes on its own schedule" [13].
What to watch
- Whether InvoiceTariff drops the sample flags from its v0.3.x MFN rows after checking them against the USITC schedule.
- Any revision to China's 12.5% tier or the 60-country table in the 2026 global Section 301 program.
- The FY2028 fee row, due when the FY2027 table expires on 2027-09-30.