Scottish Ministers have signed off a technical but important rule for the new Scottish Aggregates Tax: if the tax isn’t paid on time, interest will run from the return’s filing date. The change applies from 1 April 2026 and is designed to make the payment trigger crystal clear for operators and suppliers moving stone into Scottish projects.

The move is made by The Revenue Scotland and Tax Powers Act (Interest on Unpaid Tax and Interest Rates in General) Amendment Regulations 2026 (SSI 2026/17). The instrument was signed on 20 January 2026, laid before the Scottish Parliament on 22 January 2026, and comes into force on 1 April 2026. It inserts a new entry into regulation 4(1) of the 2015 Regulations to fix the ‘relevant date’ for Scottish Aggregates Tax at the filing date for the return, under section 217 of the 2014 Act.

In practice, ‘filing date’ is the legal deadline by which the return must be submitted. Miss that date or pay after it, and interest starts from that filing date rather than when any assessment is raised or a reminder lands. That definition is set by section 82 of the Revenue Scotland and Tax Powers Act 2014 and is now expressly cross‑referenced for Scottish Aggregates Tax in the amended regulations.

Revenue Scotland’s guidance is clear on how interest works across devolved taxes: it’s simple interest, not compound, and the late‑payment rate tracks the Bank of England base rate plus 2.5 percentage points. That framework will apply to Scottish Aggregates Tax once it goes live, meaning delays quickly carry a real cash cost for contractors and quarry groups alike. (revenue.scot)

For Northern businesses, the cross‑border angle matters. Revenue Scotland says firms based in England, Wales or Northern Ireland who sell aggregate to Scottish customers may fall within scope, depending on how and where material is commercially exploited. If you’re shipping out of Northumberland, Cumbria or County Durham into Scottish jobs, expect to engage with SAT rules rather than the UK Aggregates Levy for those supplies. (revenue.scot)

Timing is tight. The Scottish Government and Revenue Scotland state that SAT starts on 1 April 2026, replacing the UK levy in Scotland, with enrolment activity already under way. Officials have also signalled a proposed 2026–27 SAT rate of £2.16 per tonne, to be set via the Scottish Budget. Until then, the current UK Aggregates Levy still applies in Scotland. (revenue.scot)

Revenue Scotland’s own timetable has enrolment opening from January 2026, guidance in early 2026 and go‑live on 1 April 2026. If you plan to register a group, make an exempt notification, or transfer a going concern, the agency has published step‑by‑step enrolment notes to speed things along before the switch. (revenue.scot)

There’s more movement around the edges too. On 19 January 2026, parts of the 2024 Act kicked in covering set‑off, communications, automation and late‑payment penalties. Revenue Scotland has updated guidance accordingly, so finance teams should check how set‑off and penalty timings interact with SAT once returns begin. (revenue.scot)

Bottom line for Northern suppliers into Scotland: map which contracts and loads will sit under SAT from April, build the Bank Rate plus 2.5% late‑payment exposure into cashflow, and align terms with Scottish customers so payment dates and filing dates match. Given the filing date now drives interest, leaving settlement to drift past the deadline will be expensive and avoidable.