A UK accounting software price advertised today is almost never a price. It is an introductory discount — typically 70% to 90% off for six months, for new customers only, non-renewing — and it reverts to full list price on your seventh bill.
Compare on that headline and you are comparing marketing budgets, not products. The vendor running the deepest discount this month wins every comparison, and the reader is handed a number they will pay for half a year and then never again.
We therefore model total spend over twenty-four months: promotional months at the promotional rate, then full list price through to month twenty-four. Two years is the shortest window in which the promotion stops dominating the arithmetic while still being a horizon a small business can plan against. It also roughly matches how long people actually stay — switching accounting software mid-year is painful enough that most don’t.
The arithmetic, worked in the open
Xero Ignite, at the promotion running on 31 July 2026: six months at £3.20 = £19.20. Then eighteen months at £16 = £288. Two-year total: £307.20 ex VAT.
Which means the discounted period accounts for about 6% of what you will actually pay across two years. Ninety-four per cent of the bill is the number nobody puts in a headline.
Every 24-month total on this site is printed alongside the multiplication that produced it. If our arithmetic is wrong you can see that it is wrong, which is the only sort of transparency that is worth anything. Where a vendor’s promotion differs from the six-month pattern, we model its actual terms and say so.