One of the most common misreadings of Brexit is that the UK "left the Common Transit Convention". It didn't. The UK remains a full contracting party to the CTC — it was never part of the EU Customs Union in the same way it was part of the single market, and it has continued to operate its own transit system under its own NCTS instance since 1 January 2021. What did change is what moves under T1 and how the UK's NCTS talks to its EU counterpart.
Before Brexit
Before 1 January 2021, goods moving between the UK and the EU were intra-Union goods. They did not need a transit declaration to cross an internal border. T1 and T2 were used mainly for goods passing through the EU on their way to a non-EU country, or for non-Union goods already under duty suspension. Most UK-based forwarders used transit only for the non-EU leg of a route.
After Brexit
The UK is now a third country for customs purposes. Goods moving from the UK to an EU country can still use T1 to move under duty and VAT suspension — the Common Transit Convention makes that possible. The practical difference is that T1 is now a useful answer for many more UK-origin movements than it was before, particularly for:
- UK exports to an EU inland destination where you want to avoid formalities at the port of entry.
- Goods heading from the UK to a non-EU CTC country (Türkiye, Serbia, North Macedonia, Switzerland, Norway, Iceland, Ukraine, Liechtenstein) without splitting the movement at the EU border.
- Goods that entered the UK under temporary storage and need to leave again under seal.
The NCTS side
The UK runs its own NCTS. When you lodge a T1 in the UK, the declaration enters the UK NCTS, and messages are exchanged with the equivalent EU system (and with other CTC parties' systems) as the movement progresses. The important practical points are:
- The UK NCTS is a separate instance from the EU NCTS. They speak to each other, but a declaration is lodged on one or the other — not both.
- Office of departure, offices of transit and office of destination are recorded on the declaration at the point of lodgement. Changes mid-route require an amendment and acceptance by HMRC and the relevant foreign office.
- Every movement needs a guarantee that is recognised across the CTC. Most hauliers rely on a UK-issued Comprehensive Guarantee (CCG) through an authorised provider.
NCTS Phase 5
The CTC parties moved onto NCTS Phase 5 in 2024. The upgrade rolled out new message formats and more data requirements on the declaration, and most importantly, a tighter enforcement of data quality. Incomplete HS codes, missing consignee EORI, inconsistent weights — the kind of things NCTS Phase 4 would sometimes let through — are now more likely to come back as a query. That is not a reason to panic, but it is a reason to take data preparation seriously.
What this means for you
If you are moving UK exports to the EU regularly, T1 is now a mainstream tool, not an edge case. The two things that separate a smooth operation from a chaotic one are: a clean data flow into NCTS, and an active discharge-tracking discipline so guarantees release on time. The regulations have not gone anywhere — the UK is still a CTC party, the CCG still works, and the T1 still does what it always did. What has shifted is how much of your UK-EU volume it now touches.