In brief
The tax applies across the United Kingdom, including Northern Ireland. Section 144 gives each route of importation its own moment of import, tied to the customs charge that attaches to it, and section 146 names the importer on each route by the declaration. A Union good returning to Northern Ireland within three years in the state in which it left is exempt.
Chapters 2, 4 and 17 of UK CBAM for Importers cover the routes, the dates and the exemptions.
The routes
Section 144(2) of the Finance Act 2026 is the ordinary route: a good chargeable to import duty under section 1 of the Taxation (Cross-border Trade) Act 2018 is imported when liability to that duty is incurred, which at a Great Britain port is when the declaration is accepted. Section 144(3) and (6) cover goods chargeable to duty under section 30C of that Act, or that would be but for regulations, and fix the time of import at the entry of the good in Great Britain in the course of its removal from Northern Ireland. Section 144(4) covers goods chargeable under sections 30A(3) or 40A(1)(a), which charge duty on goods other than Union goods entering Northern Ireland and on the removal to Northern Ireland from Great Britain of goods that are not domestic goods; liability is incurred when a customs debt on import is incurred under the Union Customs Code as it has effect in the United Kingdom.
Four further cases
Section 144(5) lists four cases imported at the time of importation for the customs and excise Acts: a Union good that enters the United Kingdom by entering Northern Ireland and is not excluded by Treasury regulations; a good imported from the Isle of Man and not so excluded; and goods that have become domestic goods under the outward processing rules or under section 36(6) of the 2018 Act. Section 144(10) lets the Treasury exclude some goods from subsections (4) and (6) by regulations, and as at 13 September 2026 none had been made.
Who the importer is
Section 146(2) names the importer on the ordinary route and the two Northern Ireland to Great Britain routes as the person in whose name the declaration was made or on whose behalf it was made. Section 146(3) makes the same provision for goods imported under section 144(4) in the vocabulary of the Union Customs Code: the declarant, within Article 5(15), or the person on whose behalf the declaration was made. Section 146(4) provides that for the four cases in section 144(5) the importer is the person on whose behalf the good is imported.
The exemptions on these routes
Section 147(2)(c) exempts a good imported under section 144(4) where returned goods relief under Article 203 of the Union Customs Code is available, and section 147(2)(d) exempts a Union good that left the United Kingdom by removal from Northern Ireland and comes back by entering Northern Ireland within three years, in the state in which it was exported. Section 147(2)(e) exempts a good from the Isle of Man if returned goods relief would have been available. The exemptions guide covers the rest.
What to hold on to
Importation for the tax is not a new event to be identified separately. It is the customs event a business already knows on each route, and the date on the relevant declaration or customs debt is the date of importation. A business that moves covered goods into or through Northern Ireland should map each of its flows to one of the routes in section 144 and identify the declarant on each.