The Trader Support Service isn't a monolith. It's a sequence of data submissions with strict ordering: safety and security data, customs information, then movement reference.
Core entities
Every GB to NI move needs a trader EORI, party data for the consignor and consignee, a goods table with commodity codes (6 digits standard, 8 for Category 2), an at-risk flag, and a UKIMS authorisation reference where claimed.
Ordering constraints
The movement reference cannot exist before the customs entry. Build the pipeline to enforce this — do not rely on humans catching it.
The full sequence and the field-level dependencies sit in this engineer-friendly guide to TSS for GB to NI.
Where integrations usually break
Vehicle details typed twice. Container numbers absent. Trailer swaps not reflected downstream. Every one is a data-sync problem, not a customs problem.
Design recommendation
Model the eight TSS stages as a state machine. Each transition validates the payload before the next call. Reject early, log verbosely, and surface the specific failing field.
To see how iCustoms exposes this data model through an API-first customs platform, watch a demo.
