New TSS Portal Live From 20 October - What’s Changing
The Trader Support Service (TSS) supports the movement of goods between Great Britain (GB) and Northern Ireland (NI) under the Windsor Framework Agreement, helping traders complete the customs and safety declarations required for those movements. It is now entering the next stage of its long-planned digital upgrade. Since a new provider took on delivery of this next phase (as covered in our earlier update on TSS and trading with Northern Ireland), HMRC has been working towards a modernised, digital-first version of the portal- and that new system is now close to going live. From 20th October 2026, the new TSS portal will officially launch, following a four-month testing period designed to iron out issues before day-to-day use begins. From this date, all new TSS declarations will need to be started and completed on the new portal.
From 30th November 2026, HMRC will close down the ability to submit supplementary information in the current TSS system entirely. The detail that matters most for traders is what happens to their existing declarations, especially any of those submitted before 20th October but are awaiting supplementary declarations (often we refer to this as the backlog of TSS declarations). The ability to submit supplementary declarations will not be carried across to the new portal for older imports. Anything still outstanding when the winding down of the old TSS portal on 30th November will not be accessible for submission; any movements started in the old system must be completed in that system and before the cut-off date.
Given that HMRC has been paying closer attention to outstanding TSS filings, this deadline is more than a simple housekeeping exercise - it is a compliance deadline with real consequences for anyone who misses it.
Why This Matters For NI and ROI Traders
This migration affects every business moving goods from Great Britain into Northern Ireland or the Republic of Ireland through TSS, regardless of size, sector, or how frequently declarations are made. If your business has any backlog of supplementary declarations sitting in the current system, the 30th November deadline applies to you directly. The risk here goes beyond a missed administrative task. Supplementary declarations form part of the audit trail HMRC uses to confirm that duty and VAT have been correctly accounted for on goods movements.
A backlog left unresolved when the old system closes removes the opportunity to submit a supplementary declaration, which can leave a business exposed if HMRC later queries a historic movement into or out of Northern Ireland, as this is non-compliant. We’ve written before about how customs entry errors can escalate quickly if left unaddressed, and the same principle applies here: the earlier backlog is identified and worked through, the smaller the eventual risk and cost of putting it right. Leaving declarations unresolved until the final weeks before the deadline significantly increases the chance of mistakes. There is also a practical resourcing impact to consider. Compliance and logistics teams will need to learn the new portal’s processes while simultaneously working through outstanding items in the old one - a combination that can stretch already busy teams thin in the run-up to the deadline, particularly for businesses with a sizeable number of open declarations.
What Traders Need To Do Before 30 November
With a fixed deadline and SDI information not being migrated to the new platform, the priority for every TSS user is clear: get ahead of the backlog now, rather than leaving it until the final weeks before the old system closes. To prepare, businesses should:
Businesses that wait until late November risk running out of time to resolve declarations properly. That increases the chance of errors, gaps in records, and follow-up questions from HMRC further down the line - all of which are far easier to avoid than to fix after the fact.
How BKR Can Support
Clearing a supplementary declaration backlog against a fixed deadline is exactly the kind of detailed, time-pressured task that’s easy to get wrong when teams are already stretched. BKR can support TSS users by reviewing and processing outstanding declarations, working through backlogs efficiently, using our dedicated and experienced customs brokers to make sure everything is completed correctly before the old system closes – so everything is cleared and nothing is lost in the transition.
We can also help your team prepare for the new portal itself, from understanding how existing processes map across to the new system, to flagging any facilitations or simplifications you may be able to make use of. As part of a wider review, we can identify any duty or tax that may be due back to you, for example through the duty drawback scheme.
Additionally, BKR can provide bespoke in-house training sessions to staff explaining how to complete declarations, as well as completing declarations in the new system once the upcoming migration has taken place.
If you’re unsure how large your backlog is, or want support clearing it before 30th November, get in touch with the BKR team for a free consultation with one of our customs advisors.
Speak With An Advisor
Let us know a little bit about how we can help and one of our customs experts will be in touch to arrange a consultation at the next mutually convenient date.
Schedule a free 30-minute consultation with one of our Advisors today.
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