CHIEF is a proprietary application, which BT ran on the VME O/S on Fujitsu hardware. The database software is IDMSX. 

According to the HMRC website the current contract is being run by Capgemini from 2010 to 2015, then the plan was to replace the outdated COBOL and VME-based existing system, with a Service Oriented Architecture (SOA) design, which will allow integration with other CSTP and other HMRC business processes. The solution will also take advantage of COTS packages, where appropriate. Once delivered, CHIEF STE will provide a more agile solution, making future business changes easier to accommodate, whilst retaining existing response times and availability.

However, this never happened. But now  The taxmen say they are moving to the shiny new Customs Declaration Service (CDS), and they swear it will happen on 4 June 2024.

According to Computing Magazine, CHIEF has been the backbone of Blighty's border since 1994, but it's been more stop-and-go lately. The big switcheroo was supposed to happen in 2019, but let's say it's been a bit of a saga. Five missed deadlines and a whopping contract worth nearly €197.5 million (that's £168.8 million for those keeping score) later, and we're still waiting.

Brexit made things worse, with additional pressure on goods crossing the border. Post-Brexit border controls have been difficult to manage, with multiple overlapping systems requiring traders to submit information to three or more services, including CHIEF.

HMRC's promising that CDS will be the one-stop shop for all that import-export malarkey.

"The Customs Declaration Service is the UK's new single customs platform, a modern, secure IT platform supporting businesses to make import and export declarations into and out of the UK. All other customs-related systems have been integrated into CDS and will function as they did with CHIEF."

It insists that CSD reckon it's user-friendly and packed with features and it is supposed to play nice with all the other systems, so no more tech headaches.