MRN, DUCR and LRN Meaning – Formats and When Each Number Matters

MRN, DUCR and LRN come up in the same conversation very often, but they don't mean the same thing. In practice, many problems with clearance or movement to the port aren't down to a "missing number" at all, but to confusing which number belongs to which stage of the process.

This guide explains the simplest way to tell them apart and shows when these references come up during import, export and UK-EU transit. We also cover the difference between LRN, MRN and DUCR and how to track an MRN separately. If you need support with the full process, also see our UK-PL customs consultancy for import and export.

What does MRN mean?

MRN stands for Movement Reference Number. It is a reference number generated once a declaration is accepted, or as part of certain procedures such as transit. In practice, the MRN is one of the main numbers you use for the onward movement of goods, submitting documents, and checking status.

GOV.UK notes, for example, that you need the MRN from your Customs Declaration Service declaration to upload supporting documents, and HMRC asks for the MRN (or entry number) when you request certain corrections, such as amending importer details on a cleared import declaration. In transit, the MRN is also the key number for movements in NCTS.

MRN number format: what do the 18 characters mean?

According to HMRC's developer guidance, an MRN consists of 18 characters with the following structure:

HMRC's example is 23XI9876AB88901AT9. The EU export rules published on GOV.UK (explanatory notes for the Export Accompanying Document) describe the same 18-character layout: a two-digit year, a two-letter country code, a 13-character unique identifier and a final check digit. You never create an MRN yourself – if a number was made up by your own team, it is an LRN or a commercial reference, not an MRN.

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DUCR meaning: what is a DUCR number?

DUCR stands for Declaration Unique Consignment Reference. It is a unique consignment reference created by the trader themselves (following the scheme set out in HMRC guidance), not by the system. It must be unique, and the same DUCR must be supplied on all linked declarations – for example an EIDR notice of presentation and the supplementary declaration that follows it.

DUCR format

The Trade Tariff CDS guide describes the WCO-format DUCR as five parts: year, country, EORI number, a dash, and a trader reference. The year is a single digit – "5" for 2025, so "6" for 2026. The EORI must start with GB, EU or XI, and the reference part is limited to numbers, upper case letters and certain special characters. The guide gives these examples: 5GB000000000000-12345 (GB EORI, 2025) and 6FR123456789000-12345 (French EU EORI, 2026).

In CDS the DUCR is declared in data element 2/1 (previous documents) with the document type code DCR. Separately, data element 2/4 is an optional field where the declarant can record a commercial reference for their own purposes.

When is a DUCR needed in a GMR?

In the context of GVMS, the DUCR is the reference entered when creating a GMR for exports from Great Britain to the EU where a combined customs and safety and security declaration has been made. You can enter more than one DUCR in a single GMR. For imports into GB, the GMR takes the import MRN from CDS, and for common transit it takes the MRN generated in NCTS. Associated import declaration references must not be included for transit movements. For the full process, see what a GMR is and how to get one.

LRN - Local Reference Number

The LRN is a local reference number created by the declarant. It's used to track a declaration and distinguish records at the stage before the definitive system references are generated. In CDS the LRN is mandatory, can be up to 22 characters, and must be unique to the transaction and to the user within a 48-hour period – a declaration with a duplicate LRN submitted in that window will be rejected.

MRN vs DUCR vs LRN: comparison

When do you need each number: export, import and transit

• Export from GB to the EU: a DUCR for the combined export declaration goes into the GMR. A safety and security exit summary MRN is entered where an exit summary is needed.
• Import into GB: the import MRN from CDS goes into the GMR if the goods are declared in CDS.
• Common transit (NCTS): the NCTS-generated MRN is used. Our guide to the T1 document for exports from the UK to the EU shows how this works in practice.

Where most mix-ups happen

• when a company confuses a transit MRN with an import declaration MRN,
• when the wrong reference is entered for a GMR (for example an MRN instead of a DUCR on an export),
• when the operations team doesn't know whether it's working with a local number or one already confirmed by the system,
• when different parties in the process use their own shorthand without a shared vocabulary.

A practical way to approach these numbers

1. Always establish which stage of the process a given number relates to.
2. Separate local numbers from references generated by the customs or transit system.
3. For GVMS movements, check exactly which type of reference needs to be entered.
4. Don't assume that because a number "looks right" it's suitable for every stage of the movement.

Summary

MRN, DUCR and LRN play different roles. The sooner a company builds a simple, internal order around these references, the less chaos there will be during clearance, corrections and communication with the carrier. If you'd like us to sort this out in the context of your own import or export model, get in touch with us.

Official sources

• GOV.UK: Create a goods movement reference
• GOV.UK: Upload documents and get messages for CDS
• GOV.UK: Amend or cancel a CDS import declaration
• GOV.UK: Simplified Customs Declaration Process - supplementary declarations
• GOV.UK Trade Tariff: Group 2 references (DUCR, LRN)
• HMRC Developer Hub: MRN structure (18 characters)
• GOV.UK: Explanatory notes for the Export Accompanying Document (MRN format)

Related articles

• EORI number in 2026
• IPAFFS in 2026
• The T1 document in 2026
• What is a GMR and how to get one

If you'd like to work through this topic using your company's own data, send us a cooperation form and describe the planned movement of goods.

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