Section 301 China Exclusion Conforming Amendment: ACE Filing Guide

Key Points

• USTR published two Federal Register notices, 91 FR 56538 (September 2, 2026) and 91 FR 64211 (October 7, 2026), making conforming amendments to Section 301 China product exclusions.
• CBP issued updated guidance in CSMS 70261629, which supersedes the earlier CSMS 69990649, to clarify how to claim the additional conforming amendment in ACE.
• ACE functionality for accepting the conforming amendment was effective at 6:00 PM ET on October 23, 2026; entries filed before that time may need to be reviewed for correct claim codes.
• A separate ACE Production maintenance window runs from 10:00 PM ET Saturday, October 24, 2026 to 4:00 AM ET Sunday, October 25, 2026; plan filing schedules around this outage.

On this page

1. What changed: two conforming amendments to Section 301 China exclusions
2. ACE system implementation and the October 23 effective time
3. How the prior CSMS guidance is affected
4. ACE maintenance window: October 24 to 25, 2026
5. Required actions for importers, brokers, and compliance teams
6. Key references

USTR has published two conforming amendments adjusting Section 301 China product exclusions, and CBP has confirmed that ACE will accept claims under the additional conforming amendment as of 6:00 PM ET on October 23, 2026. Filers who submitted entries claiming these exclusions before that activation time should verify that their claim codes align with the updated ACE functionality described in CSMS 70261629.

The links in this article go to the primary documents: the Federal Register notices and CBP CSMS messages themselves. Read the source.

What changed: two conforming amendments to Section 301 China exclusions

On September 2, 2026, USTR published 91 FR 56538, and on October 7, 2026, USTR published 91 FR 64211. Together, these two Federal Register notices make conforming amendments to existing Section 301 China product exclusions. Conforming amendments of this type typically align the exclusion language or covered HTS subheadings with prior substantive decisions, but they carry real duty consequences: an entry that does not properly reflect the amended exclusion claim will not receive the associated relief from Section 301 additional duties.

ACE system implementation and the October 23 effective time

CBP confirmed in CSMS 70261629 that ACE functionality to accept the additional conforming amendment became effective at 6:00 PM ET on October 23, 2026. This means the system-side capability to process the updated exclusion claim codes was not available before that date and time. Filers should confirm with their software or service provider that the correct claim is transmitting successfully now that the ACE update is live.

How the prior CSMS guidance is affected

CSMS 70261629 explicitly updates and supersedes CSMS 69990649, which provided the earlier round of guidance on the Section 301 conforming amendment. If your team built filing procedures or ACE claim-code workflows based on CSMS 69990649, those procedures should be reviewed against the current message. The updated CSMS reflects the additional amendment published in 91 FR 64211 and should be treated as the controlling operational guidance going forward.

ACE maintenance window: October 24 to 25, 2026

Separate from the exclusion update, CBP has scheduled a standard invasive maintenance window for ACE Production, running from 10:00 PM ET Saturday, October 24, 2026 to 4:00 AM ET Sunday, October 25, 2026, as detailed in CSMS 70265390. During invasive maintenance, ACE Production capabilities may be unavailable or degraded. Brokers and filers with time-sensitive entries should either complete submissions before 10:00 PM ET Saturday or plan to resume after 4:00 AM ET Sunday.

Required actions for importers, brokers, and compliance teams

• Update claim-code procedures now. Pull CSMS 70261629 and compare its guidance against your current ACE filing templates. Replace any workflows built on the superseded CSMS 69990649.
• Audit entries filed before 6:00 PM ET on October 23, 2026. If you filed entries claiming a Section 301 China exclusion covered by either 91 FR 56538 or 91 FR 64211 before ACE functionality was live, confirm the claims transmitted correctly. File post-summary corrections or protests where necessary.
• Plan around the ACE maintenance window. Avoid queuing time-sensitive entries for transmission between 10:00 PM ET October 24 and 4:00 AM ET October 25, 2026.
• Monitor USTR and CBP for further conforming amendments. Two Federal Register notices in roughly five weeks suggests ongoing adjustments to the Section 301 exclusion framework; set up alerts on the Federal Register and CSMS feeds for additional changes.

Key references

• CSMS 70261629: CBP updated guidance on Section 301 China conforming amendment, superseding CSMS 69990649, effective October 23, 2026.
• CSMS 70265390: ACE Production standard invasive maintenance, October 24 to 25, 2026.
• 91 FR 56538: USTR Federal Register notice, September 2, 2026, first conforming amendment to Section 301 China exclusions.
• 91 FR 64211: USTR Federal Register notice, October 7, 2026, additional conforming amendment to Section 301 China exclusions.