ACE Certification Maintenance Windows Oct 14-17 and New Error Code 336

Key Points

• ACE Certification will be unavailable for standard invasive maintenance on October 14, 2026, from 5:00 p.m. to 8:00 p.m. ET.
• A second, out-of-cycle extended invasive maintenance window runs on October 17, 2026, from 8:00 a.m. to 9:00 p.m. ET, a 13-hour outage.
• New Cargo Release error code 336 (INVOICE/MERCH DESC REQUIRED FOR ET13) deploys to ACE Production on October 15, 2026.
• Error code 336 validates the Commercial Invoice Description in the SE40 record; entries missing this field will be flagged.

On this page

1. What changed in ACE this week
2. Maintenance window schedule and impact
3. New error code 336: what it means and which entries are affected
4. What importers, brokers, and filers should do
5. Key references

CBP is making three back-to-back changes to the Automated Commercial Environment (ACE) Certification and Production environments between October 14 and 17, 2026. Two invasive maintenance windows will interrupt ACE Certification access, and a new Cargo Release validation rule goes live in Production on October 15. Filers who do not account for the outage schedule or who submit entries missing a Commercial Invoice Description for ET13 transactions will encounter disruptions or rejections starting this week.

The links in this article go to the primary documents: the official CBP CSMS notices themselves. Read the source.

What changed in ACE this week

CBP issued three CSMS notices on October 13, 2026, covering two maintenance windows and one production deployment:

• CSMS 70190285: Standard invasive maintenance, ACE Certification, October 14, 5:00 p.m. to 8:00 p.m. ET.
• CSMS 70187331: Out-of-cycle extended invasive maintenance, ACE Certification, October 17, 8:00 a.m. to 9:00 p.m. ET.
• CSMS 70188060: New Cargo Release Condition Code 336 deployed to ACE Production on October 15, 2026.

Maintenance window schedule and impact

Both maintenance windows affect the ACE Certification environment, which is used for testing integrations, software updates, and new filing configurations before they move to Production. During an invasive maintenance window, the Certification environment is fully offline and no test submissions can be processed.

The October 14 window (5:00 p.m. to 8:00 p.m. ET) is a standard scheduled outage of three hours. The October 17 window (8:00 a.m. to 9:00 p.m. ET) is out-of-cycle and extended, running 13 hours across most of a business day. Any broker, software vendor, or filer with planned Certification-environment testing on October 17 should reschedule that work.

CBP's Production environment is not mentioned as affected by either maintenance window, so live entry filing should continue normally during those periods.

New error code 336: what it means and which entries are affected

Effective October 15, 2026, ACE Production will enforce error code 336: INVOICE/MERCH DESC REQUIRED FOR ET13. This validation rule checks that the Commercial Invoice Description field in the SE40 record is populated for ET13 entry types.

The updated Cargo Release Condition Codes document has already been posted to cbp.gov's Supporting Documents section. Filers should download the current version to confirm how error code 336 sits alongside existing codes and to update any internal validation checklists or software templates accordingly.

Entry types designated ET13 that arrive in Production on or after October 15 without a Commercial Invoice Description in the SE40 record will receive a 336 rejection. Brokers filing these entry types should verify their ACE software populates this field before the deployment date.

What importers, brokers, and filers should do

• Reschedule any ACE Certification testing planned for October 14, 5:00-8:00 p.m. ET and especially for October 17, 8:00 a.m.-9:00 p.m. ET.
• Before October 15, confirm that your ACE filing software or template populates the Commercial Invoice Description in the SE40 record for all ET13 entries to avoid 336 rejections.
• Download the updated Cargo Release Condition Codes document from cbp.gov and distribute it to filing staff and software teams.

Key references

• CSMS 70190285: ACE Certification Standard Invasive Maintenance Window, October 14, 2026, 5:00-8:00 p.m. ET.
• CSMS 70188060: New Cargo Release Condition Code 336 (INVOICE/MERCH DESC REQUIRED FOR ET13), deploying to ACE Production October 15, 2026.
• CSMS 70187331: ACE Certification Out-of-Cycle Extended Invasive Maintenance Window, October 17, 2026, 8:00 a.m. to 9:00 p.m. ET.
• CBP Supporting Documents page: Current Cargo Release Condition Codes document.