What is an MRN?
The Master Reference Number (MRN) is the unique 18-character identifier assigned to every customs declaration lodged in NCTS. It is, in effect, the customs passport number of a movement. From the moment the declaration is accepted at the office of departure until the goods are discharged at the office of destination, the MRN is the single reference that ties every NCTS message, every TAD scan, and every guarantee usage together.
Although the term Master Reference Number is most associated with transit declarations, MRNs are issued for other customs procedures too — imports, exports, safety and security declarations — each with the same 18-character structure but a different procedure context.
The structure of an MRN
An MRN is 18 characters long and follows a fixed pattern:
- Characters 1–2 — the last two digits of the year the declaration was accepted (for example, 26 for 2026).
- Characters 3–4 — the country code of the office of departure (GB for the UK, FR for France, TR for Turkey, and so on).
- Characters 5–16 — a unique system-generated reference.
- Character 17 — the procedure type indicator.
- Character 18 — a check digit calculated from the rest of the number.
The check digit is what makes the MRN self-validating: an MRN that has been mistyped will fail the check digit calculation and be rejected by NCTS before any processing takes place.
How the MRN is generated
The MRN is generated automatically by NCTS at the moment the declaration is accepted. The flow is:
- The principal (or their agent) submits the declaration data to NCTS.
- NCTS validates the data — EORI numbers, commodity codes, guarantee references, mandatory fields.
- If validation passes, NCTS accepts the declaration and issues an MRN.
- The MRN is returned to the declarant in the acceptance message and printed on the Transit Accompanying Document (TAD).
There is no manual MRN assignment and no way to choose an MRN. The number is sequential within the office of departure for that calendar year.
Why the MRN matters
The MRN matters because every downstream action depends on it:
- The driver quotes the MRN (or scans the TAD barcode) at every office of transit.
- The office of destination uses the MRN to look up the declaration data and confirm what should be on the trailer.
- The guarantee is debited and credited against the MRN.
- The discharge message is sent back to the office of departure under the MRN.
- Any enquiry, dispute, or post-clearance audit is conducted with reference to the MRN.
For traders running high volumes through UK ports, the MRN is also the primary key for internal reconciliation: every shipment in the TMS or ERP should be tagged with its MRN so that discharge can be tracked back to the originating order.
The TAD and where the MRN appears
The Transit Accompanying Document (TAD) is the printed companion to the NCTS declaration. It is produced from NCTS the moment the goods are released for transit and is carried by the driver throughout the movement.
On the TAD, the MRN appears in two places:
- As printed text in the top-right header, alongside the date and office of departure.
- As a Code 128 barcode, which is scanned at each office of transit.
Some authorised consignors print the TAD on plain paper at their own premises; others receive it from the office of departure. Either way, the document layout is standardised across the CTC area, so a TAD issued in the UK is read the same way in Calais or Cherbourg as it is in Dover or Holyhead.
Tracking a transit movement by MRN
Once a movement is open, its status can be tracked at any point. GOV.UK provides an MRN status lookup tool, and authorised users connected to NCTS via commercial software can poll the status directly through NCTS messaging.
The lifecycle statuses you will typically see are:
- Accepted — declaration is in the system, MRN issued.
- Released for transit — goods have been presented at the office of departure and released.
- In transit — the movement is open and has been recorded at one or more offices of transit.
- Arrived at destination — the goods have been presented at the office of destination.
- Discharged — the office of destination has closed the movement and the discharge message has been sent.
- Under enquiry — the time limit has expired without discharge, and HMRC has opened an enquiry procedure.
A movement that reaches discharged is closed; the guarantee is freed and no further liability attaches. A movement stuck at under enquiry is a liability the principal should resolve quickly.
What to do if the TAD or MRN is lost in transit
Losing a TAD does not lose the movement. The MRN exists in NCTS regardless of the paper document, and the goods can be matched back to the declaration electronically.
If the TAD is lost or damaged:
- The driver should contact the principal or freight forwarder immediately.
- The principal can reprint the TAD from NCTS using the MRN — the data is unchanged.
- The reprinted TAD can be presented at the next office of transit or at the office of destination.
- If the MRN itself is unknown — for example, because the driver only had the paper TAD and no electronic copy of the reference — the principal can retrieve it from the original declaration record or from the acceptance message.
The key point is that NCTS is the system of record, not the paper TAD. The TAD is a convenience for border scanning; it is not the legal basis of the movement.
Reconciling MRNs in your back office
For trader admins managing dozens or hundreds of MRNs per week, two practical habits prevent problems:
- Tag every shipment with its MRN in your internal systems at the moment the declaration is accepted.
- Run a weekly discharge reconciliation to identify any MRN that is older than its time limit but not yet discharged. These are the movements that risk turning into guarantee claims.
Help with MRN tracking and discharge
T2 Transit provides MRN tracking and discharge reconciliation as part of our managed transit service. If you would like a clean weekly view of every movement you have open, every discharge confirmation, and every exception that needs attention, talk to our team about a managed service tailored to your volume.