What is the UK Customs Declaration Service (CDS)?

HMRC describes it in one line. The Customs Declaration Service supports making import and export declarations when moving goods into and out of the UK.

Before it there was CHIEF, the Customs Handling of Import and Export Freight system. HMRC moved traders across in stages, and it took longer than the first announcement said.

• 01HMRC announced in August 2021 that import declarations would close on CHIEF on 30 September 2022, and exports on 31 March 2023;
• 02in August 2023 HMRC replaced that export date with a phased plan, moving selected high-volume declarants by 30 November 2023 and all other businesses by 30 March 2024; and
• 03HMRC’s notice to exporters set 4 June 2024 as the point after which an electronic export declaration would need to be submitted on CDS.

So there is one platform now, for imports and for exports. A procedure that still speaks in CHIEF boxes is describing a system that is not there.

One boundary. Northern Ireland movements have their own HMRC guidance and their own EORI prefix, and are not covered here.

Access is a short stack, and every layer belongs to the business that trades. It starts with an EORI number. HMRC says you need one to make customs declarations and to use customs systems such as the Customs Declaration Service. Where a business cannot apply itself, HMRC says the person it appoints gets the number instead.

Then you subscribe. HMRC asks for the sign in details used for the business or organisation, and for:

• the EORI number, which starts with GB or XI;
• the Unique Taxpayer Reference;
• the address for the business that HMRC holds on its customs records;
• the National Insurance number, for an individual or sole trader; and
• the date the business started.

HMRC says access arrives within 2 hours, or 5 working days where it needs more checks. The address must be the one HMRC already holds.

Once subscribed, HMRC says you can submit declarations using software, get postponed import VAT statements, pay Customs Duty and import VAT, and set up a Direct Debit for a duty deferment account. Declaring for somebody else needs one more thing. HMRC says whoever you hire cannot act without written instructions showing whether the agent acts directly or indirectly.

HMRC’s guidance on a full import declaration gives the short version. You need the customs procedure code, the commodity code and your declaration unique consignment reference. Alongside those it lists the departure point and destination, the consignee and consignor, the type, amount and packaging of the goods, the transport methods and costs, and certificates and licences.

The long version is organised differently. In the UK Trade Tariff completion guide every data element belongs to one of eight numbered groups.

The numbering follows the group. HMRC explains that each data element begins with the number of the group it belongs to, so the Importer Identification Number sits under group 3, Parties, as DE 3/16. Once you know that, an error code stops being a riddle.

There is no single list of required fields

Which elements are required depends on the movement type and the declaration category. HMRC points declarants at Appendix 21, Declaration Category Data Sets, for the specific elements needed for each category.

Inside a data set HMRC marks every element with a letter. A is mandatory, always required. C is optional, and HMRC says it is up to the trader to choose whether to provide it. D is dependent, required depending on the circumstances involved. Further columns say whether the element is declared at header level or item level.

So “what does the declaration need” has no general answer. It has an answer per shipment, and the letter D is where most of the chasing lives.

A declaration is not typed into a public website. HMRC’s toolkit says that if you submit declarations yourself you will need specialist software to interact with HMRC systems.

HMRC publishes a list of software developers providing customs declaration support, and is careful about what that list is. HMRC cannot recommend or endorse any one product or service over another. It groups providers by what their software supports: CDS imports, CDS exports, simplified declarations, and customs warehouse. Beyond that HMRC does not describe what the software must do, so neither does this guide.

There is a second connection. Where goods sit in a temporary storage facility, HMRC says that to link your computerised inventory system to HMRC systems you will need to join an approved community systems provider. HMRC names Cargo Community Systems UK, Community Network Services, Maritime Cargo Processing, DHL and Pentant. You can use as many as you need, but only one can be the facility stock account.

So a forwarder clearing at an inventory-linked location runs two arrangements at once: software talking to CDS, and an inventory system talking to the port. A delay can come from either, and the emails land in the same mailbox.

Accompanied trailer traffic runs on a second HMRC service. HMRC says to register for the Goods Vehicle Movement Service to get your goods through customs if you move them through a UK border location that uses it.

Who registers is broader than people assume.

• HMRC says you need to register if you import into or export from the UK through a port which uses the service;
• HMRC says a customs agent can register on your behalf; and
• to register you need an EORI number starting GB.

The output is a goods movement reference. HMRC’s description is the whole point: it links together all the declarations which have been submitted for the goods before they reach their destination. To create one you need:

• a reference for all goods in the vehicle, trailer or container, which for an EU to Great Britain import is the movement reference number from CDS;
• a vehicle registration number, if the movement is accompanied; and
• the trailer or container reference number, if it is unaccompanied.

The reference is presented at the port being left from, and HMRC says the carrier will allow you to embark if it is valid. HMRC also warns of a penalty where goods are imported at locations requiring pre-lodgement and move without enough evidence that a declaration has been made.

Read that backwards and the effect on the desk is obvious. The declaration references must exist before the movement reference can be built, and that before the driver leaves. A missing licence number stops being a customs problem at the border and becomes a haulage problem hours earlier.

The import clock depends on where the goods sit. HMRC says a full import declaration must be submitted within 90 days where temporary storage is used, and otherwise within the timescale set by the operator of the location. It may go in up to 30 days early, and is accepted only when the goods arrive.

The export clock depends on the mode. HMRC sets pre-departure timings from at least 30 minutes for air to as much as 24 hours for sea cargo that is not containerised.

After acceptance, HMRC says you will be sent a message through the Customs Declaration Service when customs have cleared the goods, and that duty must be paid before release. An export has a tail. HMRC needs a departure message to say the goods have left, which happens automatically at locations using inventory-linked systems, the Goods Vehicle Movement Service or approved loaders. Everywhere else somebody reports it.

HMRC’s answer for a pre-lodged import declaration is short. They can be rejected if there are errors in your declaration.

What comes back is an error message, DMSREJ, with specific error codes for the parts that failed validation. HMRC publishes the full list of Customs Declaration Service error codes and their descriptions, last updated on 23 June 2026.

The consequence is heavier than a resubmission. HMRC says you cannot amend a rejected declaration and must submit a new one with the errors corrected. The goods are moved to an inland border facility and released only when the new declaration is presented and cleared. The original goods movement reference stays on hold, moves to complete status after 7 days, and cannot take the new one.

HMRC does not publish a ranking of causes, so nobody honest can give you one. What it does publish is the shape of the failure: a code names a data element that did not validate. Go back through the eight groups and ask which elements depend on an answer somebody else owes you.

• a commodity code nobody confirmed, so group 6 is filled in from a description;
• a licence or certificate reference that never arrived, leaving group 2 short;
• a procedure code chosen for a regime the customer has since changed;
• a valuation built from an invoice that was superseded after the entry was drafted; and
• an EORI, authorisation or container number that moved since the last shipment.

Every one of those is a data element that failed. Every one of them started as an email answered late, answered by the wrong person, or not answered at all.

Read back through the eight groups and count how many are decisions your team makes. Very few. The rest are answers other people owe you. What the goods are, what they are worth, which licence covers them, which container they went into.

The transmission takes seconds, through software HMRC has already listed. The assembly takes days, across time zones, and is usually held together by one person remembering who has not replied.

FreighAI does not submit declarations to CDS or to any other customs system. It works on the assembly around them. Spots what is missing in an enquiry and drafts the email asking for it. Follow-ups, chasers and reminders happen on their own, on the same conversation.

The entry is still prepared and checked by the person accountable for it, and still reaches HMRC through your own software or your own broker. Two questions are worth putting to any supplier who says it helps here:

• 01Show us an import instruction with a commodity code and a licence missing. What does the system send, who does it go to, and when does it ask again?
• 02When the answer arrives four days later on a different thread, who is told, and what does a person still have to copy across by hand?