Guides / LRN explained · Updated 19 October 2026

LRN in customs: what a local reference number is and how it differs from an MRN

The LRN is the reference you give your own customs declaration; the MRN is the one the system gives back. This guide shows where each appears in CDS and NCTS, and which one the haulier actually needs.

This guide is also available in Polish.

LRN in customs: the short answer

An LRN, or local reference number, is the reference the declarant gives its own declaration. You (or your customs agent, or the declaration software) create it and send it with the declaration. The customs system then answers with an MRN, the movement reference number, which identifies the declaration officially from that point on. So the rule of thumb is simple: the LRN is yours, the MRN is the system's.

That difference matters in practice. The LRN lets you and the customs office find a declaration before an MRN exists, and it keeps your own records tidy. The MRN is what hauliers, border systems and later declarations refer to. Mixing the two up is a common cause of failed check-ins and confused emails.

The local reference number on a customs declaration in CDS

For UK import and export declarations made in the Customs Declaration Service (CDS), HMRC's technical glossary says the LRN is defined by the declarant and submitted in Data Element 2/5. It must be unique for a period of 2 days from the point the declaration is accepted, and it can only be reused once those 2 calendar days have passed.

The same glossary describes the MRN as a globally unique identifier for a declaration, assigned by CDS once a declaration is submitted. In other words, you never choose the MRN; you only choose the LRN that travels with your submission.

HMRC's glossary also defines a third reference that people often confuse with the LRN: the DUCR, which is assigned by the declarant to uniquely identify a single consignment of goods. The DUCR is about the consignment; the LRN is about one particular declaration you are sending.

The LRN in NCTS transit declarations

Transit is where the LRN does the most visible work, because there is often a gap between lodging the declaration and getting an MRN.

Creating it

GOV.UK's guidance on moving goods out of Great Britain using transit lists the local reference number among the things you need before you submit a transit declaration, describing it as a unique number of less than 22 characters that you create yourself. HMRC's Transit Manual Supplement puts it slightly differently: the format is left to the declarant's discretion, provided it is unique and does not exceed 22 characters. The Supplement also says an LRN can be reused if it was previously entered on an NCTS declaration that was rejected.

Presenting the goods

When the goods are presented at the office of departure, the presenter needs to give the LRN that was included in the declaration. The Supplement stresses that this is especially important when a transit declaration is pre-lodged, because the LRN is then the only reference the officer can use to recall the declaration on NCTS. It also notes that an LRN can only be recalled by the office of departure entered on the declaration, except when goods are presented at inland border facilities for departure.

When the MRN appears

Under the normal procedure, the Supplement explains that the MRN (sent in the IE028 message) is only generated after the goods are presented at the office of departure. Until then, NCTS holds the declaration in a submitted state rather than accepting it. For authorised consignors using the simplified procedure, the system can accept the declaration and generate the MRN automatically.

Once the movement is under way, the reference that matters is the MRN. HMRC notes that the paper transit accompanying document no longer has to travel with the goods, but the presenter or driver must have the MRN for the movement. For a fuller walk-through of a T1 movement, see our guide to T1 transit from the UK to the EU.

LRN vs MRN vs DUCR at a glance

Reference	Who creates it	What it identifies	Where you meet it
LRN	The declarant	One declaration, before and alongside the official reference	CDS Data Element 2/5; NCTS declarations; presentation at the office of departure
MRN	The customs system	The declaration or movement, officially	Hauliers' paperwork, GVMS, later declarations
DUCR	The declarant	A single consignment of goods	Export declarations and GVMS on GB to EU routes

Where the LRN does not go

At GVMS ports, the haulier links the crossing to the customs declarations through a goods movement reference. GOV.UK's list of declaration types in GVMS says that for an import declaration the MRN is the reference added to the GMR, and for an export declaration it is the DUCR. The LRN is not listed as a reference for those declaration types, so do not hand a driver an LRN in place of an MRN. Our guide to the movement reference number covers which MRN goes into the GMR on each route.

The same idea on the EU side

The LRN is not a UK invention. Poland's customs declaration completion instructions for AIS/IMPORT PLUS, AES/ECS2 PLUS and NCTS2 PLUS describe it as a local reference number assigned by the person lodging the declaration to identify each declaration, and map it to box 2/5. Poland's NCTS2 PLUS user guide shows the same sequence as the UK: when a transit declaration is technically and formally correct, the declarant receives an IE928 message confirming the data has been saved, and at that stage the LRN is what identifies the declaration. After the declarant sends the IE170 presentation notification, it receives the IE028 message with the MRN. If a pre-lodged declaration is not followed by the presentation message within 30 days, it is rejected.

Practical tips

Use a consistent LRN scheme you can trace back to your own job or order number.
Keep LRNs within 22 characters for transit and never reuse one inside the CDS 2-day window.
If you pre-lodge a transit declaration, make sure whoever presents the goods has the LRN.
Pass the MRN, not the LRN, to the haulier once the system has issued it.
Store the LRN, MRN and DUCR together in your records so any later query can be matched quickly.

Easy Clearance has a short explainer on what an LRN is and where it appears, written from the point of view of UK–Poland road movements.

Related guides

Sorting out declaration references?

Easy Clearance is a UK–EU customs clearance agency handling import and export declarations, T1/T2 transit and UK–Poland removals. Its LRN page sums up the difference between LRN and MRN.

Read the LRN explainer

Sources

General information, not legal, tax or customs advice. Rules change; confirm current requirements on gov.uk or with a registered agent before you ship.