Post-Brexit customs — the CDS (Customs Declaration Service)

Before Brexit, selling from London to Paris required no customs formality. Since 1 January 2021 it is import/export, and every movement of goods must be the subject of an electronic declaration. The CDS (Customs Declaration Service) is the system that processes these declarations; it replaced the older CHIEF in 2023. The special case of Northern Ireland is governed by the Northern Ireland Protocol, revised by the 2023 Windsor Framework.

History — from CHIEF to CDS, and Brexit

The CHIEF system (Customs Handling of Import and Export Freight) processed UK customs from 1994 to 2023 — a near-monolith, reliable but ageing. From 2018, HMRC began its replacement with the CDS, more modern and aligned with the Union Customs Code (UCC).

Brexit sharply accelerated the stakes: from 1 January 2021, GB-EU trade became import/export operations subject to declaration. Volumes exploded. CHIEF closed for imports on 30 September 2022, then for exports on 31 March 2023; CDS became the single system. In parallel, the Windsor Framework (27 February 2023) revised the Northern Ireland Protocol to smooth GB→Northern Ireland flows via a "green lane".

1994       | CHIEF (Customs Handling of Import and Export Freight), the
           | historical UK customs system, goes live.
           |
2018       | HMRC announces the gradual replacement of CHIEF by the CDS
           | (Customs Declaration Service), aligned with the Union Customs
           | Code and technically more modern.
           |
2021-01-01 | Brexit takes effect on customs. GB-EU trade becomes
           | import/export; declaration volume rises sharply, EORI now
           | indispensable.
           |
2022-09-30 | CHIEF closes for import declarations — mandatory switch to
           | CDS for imports.
           |
2023-03-31 | CHIEF closes for export declarations — CDS becomes the UK's
           | single customs system.
           |
2023-02-27 | Windsor Framework agreed, revising the Northern Ireland
           | Protocol: "green lane" (goods staying in the UK) and "red
           | lane" (goods at risk of entering the EU).
           |
2024-2026  | Rollout of border controls (Border Target Operating Model,
           | BTOM) on EU→GB imports in phases, and CDS stabilisation.

Governance — HMRC Border Force

The CDS is operated by HMRC, in conjunction with the Border Force (frontier control) and the Cabinet Office for border strategy. Declarations are filed by operators or their customs representatives (freight forwarders, brokers) via software connected to the CDS API. HMRC publishes a voluminous CDS Declaration Completion Guide detailing each data element.

The rollout of physical controls on EU→GB imports follows the Border Target Operating Model (BTOM), phased by sanitary and phytosanitary risk category from 2024.

Technical schema — CDS declaration

The CDS adopts the data elements structure of the Union Customs Code (e.g. DE 3/16 for importer EORI), richer than CHIEF's old "boxes". A declaration references the EORI, country of origin, the commodity code (Combined Nomenclature CN8) and the calculation of import duty and VAT.

CDS import declaration (extract of Data Elements, UCC format)

DE 1/1  Declaration type            IM    (import)
DE 1/2  Additional type             A     (standard declaration)
DE 2/1  Previous declaration        Z-ZZZ-...
DE 3/16 Importer EORI               GB123456789000
DE 3/18 Declarant EORI              GB987654321000
DE 5/15 Country of origin           FR
DE 6/8  Goods description           Automotive parts
DE 6/14 Commodity code (CN8)        87089997
DE 4/3  Tax calculation             B00 (VAT) / A00 (duty)
DE 8/5  Nature of transaction       11
Movement reference (GMR)            GMRA0000000001  (Goods Movement Ref)

• EORI — mandatory importer/exporter identifier (GB or XI).
• CN8 commodity code — 8-digit tariff classification (UK Global Tariff).
• UCC data elements — standardised structure (DE 1/1, 3/16, 6/14…) shared with the EU model.
• GMR — Goods Movement Reference, aggregating movements via the GVMS service at "inventory-linked" ports.
• Postponed VAT Accounting — import VAT can be reverse-charged on the MTD return rather than paid at the border.

CDS vs CHIEF vs EU customs

Adoption — GB, Northern Ireland, Windsor Framework

• Full switch to CDS — since March 2023, all import and export declarations go through the CDS.
• EORI generalised — every business trading with the EU had to obtain a GB EORI; Northern Ireland flows often require an XI EORI.
• Green/red lanes — the Windsor Framework structures GB→Northern Ireland flows since 2023, reducing controls on goods staying in the UK.
• Phased BTOM — sanitary controls on EU→GB imports roll out gradually from 2024.

Common pitfalls

• CHIEF reflexes on CDS. CHIEF "boxes" do not map one-to-one to CDS UCC data elements; a direct mapping fails.
• Missing or wrong EORI. Without a valid EORI (and XI for Northern Ireland), the CDS declaration is rejected.
• Inaccurate commodity code. A wrong CN8 distorts duty and VAT; check the UK Global Tariff, which diverges from the EU tariff.
• Forgetting Postponed VAT Accounting. Paying VAT at the border instead of reverse-charging via MTD needlessly hits cash flow.
• Confusing green and red lane. Declaring an EU-risk good in the green lane is a Windsor Framework non-compliance.

Cross-links

• United Kingdom hub — full view
• Identifiers — EORI, VAT, Companies House
• UK VAT regimes
• UK automotive EDI — post-Brexit supply chain
• gov.uk — Customs Declaration Service
• gov.uk — Windsor Framework