Starting at 6 p.m. ET tonight, Oct. 23, 2026, U.S. Customs and Border Protection's Automated Commercial Environment (ACE) will begin accepting a piece of paperwork most importers have never had reason to learn about: a "conforming amendment" tied to a Section 301 China tariff exclusion (CBP CSMS #70261629).
It sounds like backend plumbing, and mostly it is. But if you've imported certain pump parts, plastic components, or machine parts since July 1 and paid Section 301 duty on them, this fix is worth ten minutes of your time — because for months, CBP's own systems may not have recognized that those goods were still excluded.
It's a narrow fix on its face: five exclusion notes, a handful of obscure ten-digit codes. But the mechanism behind it isn't narrow at all. Every time the U.S. International Trade Commission revises the Harmonized Tariff Schedule's statistical suffixes — which happens on a recurring cycle, independent of any tariff decision — any Section 301 or Section 232 exclusion tied to the old suffix needs its own separate fix from USTR and CBP before ACE recognizes it. Until that catches up, the exclusion exists on paper but not in practice.
Why it matters
The Harmonized Tariff Schedule's ten-digit statistical suffixes — the exact code that goes on an entry summary — get revised periodically by the U.S. International Trade Commission, independent of any tariff policy change. When a suffix changes, a Section 301 or Section 232 exclusion written against the old code doesn't automatically follow the goods to the new one. The product is still supposed to be excluded; the paperwork just hasn't caught up yet. Until the Office of the U.S. Trade Representative issues a conforming amendment pointing the exclusion at the new suffix, and CBP builds that mapping into ACE, an importer filing under the new code risks having Section 301 duty assessed on goods that were never meant to lose their exclusion in the first place (Federal Register). The exclusions themselves are discretionary relief — USTR grants, extends, and can let them lapse under the authority Congress gave the Trade Representative in 19 U.S.C. § 2411 — and none of that changes here. This is purely a classification-matching problem sitting on top of exclusions that were never revoked.
The details
This particular gap traces back to a routine HTSUS update that took effect July 1, 2026, which changed the ten-digit statistical suffixes on several product lines covered by existing Section 301 China exclusions. USTR caught up with four of the five affected exclusion notes in a Sept. 2 notice (Federal Register), and CBP built that mapping into ACE via CSMS #69990649, effective Sept. 23 (GHY International). The fifth note didn't get its conforming amendment until Oct. 7 (Federal Register) — and tonight's 6 p.m. ACE cutover is CBP finally catching up on that one (CBP CSMS #70261629).
In plain terms: goods previously classified under HTSUS 8413.91.9065, .9085 or .9096 (certain pump and liquid-handling parts) now file under 8413.91.9039, .9046, .9059 or .9099; a plastics line previously under 3926.90.9910 now splits into 3926.90.9915 or .9920; and a machine-parts line previously under 8479.90.9596 now sits at 8479.90.9591 — all retroactive to July 1, 2026 (CBP CSMS #70261629). All five still sit under the same Chapter 99 exclusion heading, HTSUS 9903.88.69; only the underlying ten-digit code moved. CBP's guidance is explicit that importers claiming the exclusion shouldn't also submit the regular Section 301 duty number on the same line — it's one or the other, not both (CBP CSMS #70261629).
The refund mechanics aren't exotic. A Post Summary Correction lets an importer or broker amend an entry summary — including the duty-exclusion claim — before CBP liquidates it, and it's the quickest way to recover duty paid in error. Once an entry liquidates, the PSC window closes and a formal protest under 19 U.S.C. § 1514 becomes the only path, filed within 180 days of liquidation. CBP's own guidance on this conforming amendment points importers toward exactly that two-step sequence (CBP CSMS #70261629).
THE CONFORMING AMENDMENT, AT A GLANCE
What changed. The ten-digit HTSUS statistical suffixes for five Section 301 China exclusion notes shifted on July 1, 2026 — a routine USITC schedule update, not a new tariff action.
Two Federal Register notices. USTR conformed four of the five exclusions on Sept. 2 and the fifth on Oct. 7.
Refund path. Section 301 duty assessed on an affected entry can be recovered with a Post Summary Correction, or a protest if the PSC window has already closed.
Tonight's cutover. ACE begins accepting the fifth exclusion's new code at 6 p.m. ET, Oct. 23, 2026.
What to do about it
Check your HTS codes. If you import under 8413.91.90xx pump or liquid-handling parts, 3926.90.99xx plastic articles, or 8479.90.95xx/91 machine parts and claim a Section 301 exclusion under heading 9903.88.69, confirm you're filing under the post-July 1 ten-digit suffix.
Look back at entries since July 1. If you filed under an affected code before CBP's ACE guidance caught up — before Sept. 23 for four of the exclusions, before tonight for the fifth — and Section 301 duty was assessed, that duty may be refundable.
File a Post Summary Correction first. It's the faster path while the entry's still open. Once that window closes, a protest of the liquidation is the fallback, filed within 180 days of liquidation (19 U.S.C. § 1514).
Don't double-file. CBP's guidance is explicit: don't submit the regular Section 301 duty HTSUS number on the same line as the Chapter 99 exclusion heading — pick one.
Put HTSUS revisions on your compliance calendar. Statistical suffixes change periodically even when tariff policy doesn't. If your classification relies on a Section 301 or Section 232 exclusion, check whether your code moved at the last revision — and whether USTR has actually caught up with a conforming amendment yet.
Keep an eye on
This is the second time in two months CBP has had to push a conforming amendment through ACE for this same exclusion family, and it's unlikely to be the last time a routine HTSUS revision strands an existing exclusion. Anyone leaning on Section 301 or Section 232 relief is worth keeping an eye on USTR's Federal Register notices and CBP's CSMS feed for the next one — the gap between when a code changes and when the exclusion catches up is exactly where opportunities like this one hide.
Got questions? Drop a comment below. Ask our licensed customs brokers, and they'll get right back to you here in the comments.
THE TRADE TALK DESK
Trade, tariffs, and duties — explained plainly.