Scotland has signed off a technical but important change ahead of the Scottish Aggregates Tax go‑live on 1 April 2026: late‑payment interest on unpaid SAT will run from the return’s filing date. This clarifies the “relevant date” in Revenue Scotland’s interest rules for the new tax. (gov.scot)

Filing date has a precise legal meaning. Section 82 of the Revenue Scotland and Tax Powers Act 2014 defines it as the date by which the return must be made. Put simply: miss that deadline and interest starts accruing from that day. (legislation.gov.uk)

For planning, remember how Revenue Scotland calculates interest. Late‑payment interest is simple interest at the Bank of England rate plus 2.5 percentage points; since 24 December 2025 the published late‑payment rate is 6.25% and the repayment rate is 3.75%, both of which will move with changes in Bank Rate. (revenue.scot)

Who is in scope? SAT applies to quarry operators and others who commercially exploit aggregate in Scotland, as well as importers and intermediaries selling into Scotland. Businesses operating on both sides of the border will need a Revenue Scotland SAT registration for Scottish activity and must remain registered with HMRC for activity elsewhere. (revenue.scot)

Administration is already under way. Enrolment opened in January and Revenue Scotland says processing an SAT enrolment to the point you can create a SETS account typically takes three to four weeks, with full guidance due early 2026 and go‑live on 1 April. (revenue.scot)

What this means for cashflow. Take a mid‑sized quarry with 60,000 tonnes in a quarter. At the Scottish Government’s proposed 2026‑27 rate of £2.16 per tonne that’s a liability of about £129,600; pay 10 days late at a 6.25% late‑payment rate and the interest comes in around £220. The numbers are not huge, but repeat slippage eats into margin and will sit alongside any late‑payment penalties. (gov.scot)

The filing‑date rule is consistent with how interest works across devolved taxes. In effect, SAT now gets the same treatment in the table at regulation 4 of the 2015 interest regulations, with a new entry specifying the filing date as the trigger point for late‑payment interest. (gov.scot)

For finance teams the practical jobs are straightforward. Align invoice cycles and accruals with the return due date, build a small SAT buffer into month‑end cash planning, and avoid cutting it fine-the interest clock starts on the filing date. If your operations straddle Scotland and the rest of the UK, map separate registrations and returns into your systems from the outset. (revenue.scot)

Finally, keep an eye on the interest‑rate page that Revenue Scotland maintains and budget on the basis that movements in Bank Rate will feed directly into late‑payment costs. Because interest is simple rather than compound, clearing most of the liability quickly still reduces the cost of any shortfall. (revenue.scot)