On December 19, 2019, in Cargo Systems Messaging Service (CSMS) #41052359, U.S. Customs and Border Protection (CBP) and the U.S. Fish and Wildlife Service (FWS) released the implementation guide for submitting FWS entry data. 

The current schedule for FWS in the Automated Commercial Environment (ACE) is:

• March 2, 2020: FWS code becomes available in CBP’s certification environment;
• April 4, 2020: FWS Production Pilot begins;
• October 2020: FWS tariff flags become enforced in production for all filers.

A Federal Register Notice with additional details on the pilot will be forthcoming.

CSMS #41052359 can be found here:

https://content.govdelivery.com/bulletins/gd/USDHSCBP-27268c7?wgt_ref=USDHSCBP_WIDGET_2?utm_source=google&utm_medium=google&utm_term=(not%20provided)&utm_content=undefined&utm_campaign=(not%20set)&gclid=undefined&dclid=undefined&GAID=340499347.1568239941

The FWS Implementation Guide can be found here:

https://www.cbp.gov/document/guidance/us-fish-and-wildlife-service-ace-requirements