NCTS Phase 5 – what changed for importers and customs agents in the UK [2025]

NCTS (New Computerised Transit System) is the electronic backbone of the entire transit procedure under the CTC Convention — without it no T1 or T2 movement can be formally opened or closed. When NCTS undergoes an upgrade, every participant in the supply chain feels it: customs agents, freight forwarders, importers, Authorised Consignee warehouse operators, and declarant software vendors. NCTS Phase 5 is the largest update to this system in years — it introduces new data fields, changes the format of key reference numbers, and replaces legacy electronic messages with new versions. In the United Kingdom, HMRC completed the migration to Phase 5 in February 2024. If you operate transit through the UK or open T1 movements with the UK as the country of departure, you need to know exactly what has changed — and whether your IT systems have kept pace.

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What is NCTS and why does Phase 5 matter?

NCTS is a computerised transit management system that replaced paper transit documents (TIR carnets and T-documents) in CTC countries. Every T1 declaration opened electronically, every arrival notification, every closure of a transit procedure — all of this is handled through NCTS.

Phase 5 is an update to the system's technical specification, driven by changes in EU legislation (the Union Customs Code Implementing Act — IA) and the need to harmonise with EU systems following Brexit. The update covers: - A new set of electronic messages (IE messages) - A revised MRN (Movement Reference Number) format - New mandatory data fields in declarations - A revised amendment (correction) procedure - New validation rules on the NCTS side

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When did the UK migrate to NCTS Phase 5?

In the United Kingdom, HMRC carried out the migration to NCTS Phase 5 in February 2024. The migration was phased:

Stage	Date	Scope
Soft launch	October 2023	Pilot with selected customs agents
Full migration	February 2024	All new T1/T2 declarations in Phase 5
Phase 4 switch-off	April 2024	Phase 4 stopped accepting new declarations

EU member states carried out their own migrations in 2024, with varying dates per country. This means that transit movements opened in Poland and closed in the UK must be handled through Phase 5 on both sides of the border.

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The new MRN format — 18 characters, different structure

One of the most visible changes in NCTS Phase 5 is the new MRN (Movement Reference Number) format — the identifier assigned to every transit movement.

Phase 4 format (legacy): - 18 alphanumeric characters - Structure: 2 digits (year) + 2 letters (country code) + 14 characters

Phase 5 format (new): - 18 alphanumeric characters — same total length - Revised internal structure: different arrangement of identification elements - Key change: the Phase 5 MRN includes an additional system-version identifier

In practice this means that IT systems on the receiving side (Authorised Consignee) must correctly parse the new MRN format. Systems that have not been updated may reject or incorrectly process Phase 5 numbers, causing errors in IE007 and IE044 messages.

Practical note: Drivers and warehouse operators often write the MRN by hand on transport documents (CMR). The new format looks similar to the old one, which can lead to confusion between Phase 4 and Phase 5 numbers. If in doubt — check the year the declaration was opened: all movements opened after February 2024 in the UK are Phase 5.

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New IE messages — what replaced what?

NCTS Phase 5 introduces a new set of electronic messages. Many of the existing IE messages (IE = International Entity message) have been replaced by new versions or completely restructured.

Operation	Phase 4	Phase 5	Change
Opening a T1 declaration	IE015	IE015 (updated)	New data fields
System response after submission	IE028	IE028	Revised structure
Rejection notification	IE016	IE056	New message number
Arrival notification (AC)	IE007	IE007 (updated)	New mandatory fields
Arrival acceptance confirmation	IE008	IE008	Minor changes
Unloading (AC)	IE044	IE044 (updated)	Extended discrepancy field
Transit closure	IE025	IE025	Changed trigger
Amendment to declaration	IE013	IE013 + IE004	New approval procedure

Most important operational change — the amendment procedure:

In Phase 4, a correction to an open T1 declaration (amendment) could be submitted relatively freely before the goods arrived. Phase 5 introduced a formal amendment approval procedure: the NCTS system sends an IE004 message (Amendment Acceptance/Rejection) and the principal must wait for acceptance before continuing operations. A rejected amendment requires a new submission.

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New mandatory data fields in a Phase 5 declaration

NCTS Phase 5 expands the range of data required when opening a transit declaration. Many fields that were optional in Phase 4 have become mandatory.

New mandatory fields in the Phase 5 IE015:

• Additional declaration type — distinguishes between standard transit and simplified procedures
• LRN reference number — the Local Reference Number must be unique within the principal's system
• Seal data — a full description of seals (count and identifiers) is now mandatory
• Transport Equipment — containers/trailers must have goods items linked at item level (item-level linkage)
• Mode of transport code — more granular classification than in Phase 4
• Additional goods information — including special cases (dangerous goods, temperature-controlled)

These changes require declarant software to apply extended client-side validation — errors in the new fields result in immediate rejection (IE056) by NCTS.

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Impact on declarant software — what IT systems had to update

The migration to Phase 5 required extensive updates to declarant software on the part of all NCTS users. This applies to large platforms (such as CHIEF/CDS in the UK) as well as niche systems used by smaller customs agents.

Scope of required software changes:

1. New XML schemas — all IE messages had to be rewritten in accordance with the new NCTS5 technical specification (available on the Europa/HMRC portal)
2. New field validation — systems had to add validation rules for the new mandatory fields
3. New MRN parsing — the revised MRN format required updates to functions that process NCTS responses
4. Amendment procedure — full reimplementation of the correction approval flow (IE013 → IE004 → acceptance or rejection)
5. New error codes — updated error message dictionary (IE056 replacing IE016)

UK declarant software providers were required to update their systems before February 2024. However, some smaller systems or in-house IT solutions may not have met the deadline — with serious operational consequences.

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What to do if your IT system is not updated to Phase 5

If your declarant software provider has not migrated to Phase 5, operating through NCTS in the UK is effectively impossible — the system will reject declarations using legacy message formats.

Diagnostic steps:

1. Ask your software provider for the Phase 5 update date and the current software version number
2. Verify that the system accepts MRNs in the new format
3. Test submission of a test declaration in the NCTS test environment (UK Government Gateway)

Options if the system is not updated:

Option	Implementation time	Cost
Update from existing provider	2–8 weeks	Per provider's price list
Migration to another platform	4–12 weeks	£500–£5,000 implementation
Outsource declarations to a customs agent	Immediate	£40–£100 per declaration

Outsourcing to a customs agent is the fastest option and requires no IT investment — the agent uses their own Phase 5 system and opens T1 as your customs representative.

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Common errors after migrating to Phase 5

In the first months after the Phase 5 migration in the UK, a number of recurring operational errors were recorded.

Error 1 — Legacy MRN format entered into GMR

Operators accustomed to Phase 4 entered the old MRN format into GVMS when creating a GMR. GVMS validates the MRN against NCTS — a format mismatch caused the GMR to be rejected, preventing entry to a GVMS port in the UK.

Error 2 — Sending IE515 instead of IE015

Some unupdated systems sent the IE515 message (legacy Phase 4 format) instead of IE015 (Phase 5). NCTS rejected such declarations with an error message indicating an invalid message type.

Error 3 — Missing Transport Equipment field with multiple goods items

The new Phase 5 requirement to link goods items to transport units (container, trailer) was overlooked by operators unfamiliar with the new requirements. The result: declaration rejection or the need to submit an amendment.

Error 4 — Submitting an amendment without waiting for IE004

Operators carrying over Phase 4 habits would submit an amendment and immediately continue the operation. In Phase 5, an amendment must be approved (IE004) before further steps can be taken — skipping this procedure caused inconsistent declaration states within NCTS.

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Where to report a technical issue with NCTS

If you encounter a technical error in NCTS on the UK side, there are several reporting channels:

HMRC NCTS Helpdesk: Available through Government Gateway — organisation profile — "Transit" section. HMRC accepts submissions on working days between 08:00 and 18:00.

CTC Helpdesk Europe: For cross-border issues (e.g. a movement opened in Poland that cannot be closed in the UK) — submit through the TAXUD portal or directly to the destination customs office in the UK.

Phase 5 technical documentation: HMRC publishes the technical specification and XML schemas on gov.uk under "New Computerised Transit System: trader guide". Software providers should use this documentation when updating their systems.