What is an MRN Number in UK Customs? Complete Guide 2026

If you move goods between the UK and the EU, sooner or later you will need an MRN number. The Movement Reference Number is one of the most important codes in the UK customs system — without it, a declaration is not registered and a truck can be turned away at the border. This 2026 guide explains what an MRN number is, its exact format, when it is issued, how it differs from a GMR, and how to check one.

What is an MRN Number?

An MRN (Movement Reference Number) is, in HMRC’s own words, “a globally unique identifier for a declaration assigned by CDS once a declaration is submitted.” In plain terms: the moment your customs agent files a declaration in the Customs Declaration Service (CDS), HMRC issues one MRN that confirms the declaration is registered and being processed. CDS generates an MRN automatically for every import and export declaration, including pre-lodged declarations submitted before the goods arrive.

MRN Number Format Explained

An MRN is exactly 18 characters long, made up of letters and numbers. According to HMRC’s CDS Movement Reference Number guide, it breaks down as follows:

• Year — the current year as two digits (for example, 2026 becomes 26)
• Country code — the two-character code for where the declaration was made; for the United Kingdom this is GB
• Reference — a 14-character alphanumeric string randomly generated by CDS

So a UK MRN issued in 2026 follows the pattern 26GB + 14 characters. If a number you have been given is not 18 characters, or does not start with a year and a country code, it is not a valid CDS MRN — double-check it before presenting it at the border.

When Do You Get an MRN Number?

An MRN is generated at the moment a declaration is submitted. In a typical UK–Poland movement you may see more than one:

• Export MRN — issued when your agent submits the export declaration in HMRC CDS before the goods leave the UK.
• Import MRN — issued when the import declaration is filed in the destination country’s system (for example Poland’s PUESC).
• Transit MRN — issued when a T1 transit procedure is opened in the New Computerised Transit System (NCTS). If your goods travel under transit, a broker such as this UK–EU transit and T1 clearance service opens the NCTS movement and returns the transit MRN to your driver.

MRN vs GMR — What’s the Difference?

These two references are frequently confused, but they do different jobs:

• MRN — identifies the customs declaration (what goods you are moving and under which procedure).
• GMR (Goods Movement Reference) — identifies the vehicle crossing in the Goods Vehicle Movement Service (GVMS). For an import, the MRN is added into the GMR. The driver needs the GMR to check in at GVMS ports such as Dover, Folkestone or Holyhead.

HMRC is clear that goods cannot move on GVMS routes without a valid GMR, and a vehicle will be turned away at check-in if the GMR is missing or the vehicle, trailer or container details do not match. Both the MRN and the GMR are normally prepared by your customs agent before the truck departs and sent to the driver in minutes. For a deeper look at the declaration behind the MRN, see our guide to UK export declarations in CDS.

How to Check an MRN Number (UK MRN Checker)

There is no single public “UK MRN checker” website where anyone can type a number and see full declaration details — access to declaration data is restricted to the trader and their appointed agent. You can, however, check the status of a movement in the systems where the MRN was issued:

• UK export or import declarations — viewed in HMRC CDS or in the commercial customs software used to file the declaration.
• Transit movements — tracked through NCTS.
• Import declarations abroad — for Poland, in the PUESC / e-Klient portal.

A status of “Released” means the goods have cleared customs and can be collected from the customs-controlled area. Your customs agent can pull this status for you and confirm the goods are free to move.

What to Do if an MRN Is Not Working

If an MRN appears invalid or a movement is stuck, check the basics first: confirm the number is 18 characters, that it has not been mistyped, and that it matches the correct leg of the journey (export, import or transit). If the declaration was pre-lodged, remember it only becomes “arrived” once the goods physically reach the frontier. When in doubt, ask the agent who filed the declaration — they can see the live status in CDS and reissue documents if needed.

MRN Number Checklist

• ☐ Confirm the MRN is exactly 18 characters (year + GB + 14 characters for UK).
• ☐ Match each MRN to its leg: export, import or transit.
• ☐ For GVMS routes, make sure the MRN is added into a valid GMR before the driver checks in.
• ☐ Verify vehicle, trailer and container details match the GMR.
• ☐ Track the declaration status and wait for “Released” before collection.
• ☐ Keep every MRN on file — HMRC may ask for it during post-clearance checks.

Mini-FAQ: MRN Numbers

How long is an MRN number? An MRN is 18 characters long — two digits for the year, a two-character country code (GB for the UK) and a 14-character alphanumeric reference generated by CDS.

Is an MRN the same as a GMR? No. The MRN identifies the customs declaration; the GMR identifies the vehicle crossing in GVMS. For imports, the MRN is included inside the GMR.

Who issues the MRN? HMRC’s Customs Declaration Service (CDS) issues it automatically the moment a declaration is submitted.

Can I look up someone else’s MRN? No. Declaration data is only available to the trader and their appointed customs agent; there is no open public MRN lookup.

Do I get a new MRN for every shipment? Yes. CDS issues a unique MRN for every declaration, so a single UK–Poland trip can involve separate export, transit and import MRNs.

Sources (gov.uk)

• HMRC — CDS Movement Reference Number (MRN) guide
• GOV.UK — Create a goods movement reference (GVMS / GMR)

Customs procedures change. Always confirm current requirements on gov.uk before acting on them.