Customs Declaration Service (CDS) is the UK government’s new electronic system for handling customs declaration processes. CDS is replacing the Customs Handling of Import and Export Freight (CHIEF) system, which is closing down on March 31, 2023.
HMRC is implementing the system transition from CHIEF to CDS in several stages – with final deadlines for import declarations in September 2022 and for export declarations in March 2023.
You can learn more about it in this article or on the UK government website.