What is the final declaration?

Four quarterly updates a year are the visible part of Making Tax Digital (MTD), but they don’t finish anything. The job that finishes the year is the final declaration, and it’s the one that decides what tax you actually pay.

What it replaces

For businesses inside MTD, the final declaration takes the place of the Self Assessment tax return. Same moment in the year, same 31 January deadline, same purpose: you confirm that your figures for the tax year are complete and correct, and HMRC works out the tax. What’s changed is that most of the numbers are already there, carried up from the quarterly updates you’ve been filing all year.

What it settles that quarterly updates don’t

A quarterly update is only your business income and expenses, sent as raw totals. Your actual tax position needs a good deal more, and all of it lands here:

• Everything that isn’t this business: employment income, dividends, savings interest, pensions, other property.
• Accounting adjustments: capital allowances, private-use splits, costs that aren’t allowable, stock valuations.
• Reliefs and allowances: the personal allowance, pension and Gift Aid relief, losses brought forward, the marriage allowance.
• Your declaration that the whole picture is right, which is the bit that carries legal weight.

That’s why nothing you file in a quarter is final, and why a mistake in one is so cheap to fix. Updates are cumulative, so a correction carries forward on its own, and the final declaration is where the year is actually closed.

When is the first final declaration due?

The first-ever final declaration covers the 2026-27 tax year and is due by 31 January 2028. After that it’s every 31 January, for the tax year that ended the previous 5 April. Your tax payment is due the same day.

The soft landing never covered it

HMRC isn’t issuing penalty points for late quarterly updates in 2026-27. That easing has never applied to the final declaration: a late one earns a penalty point, and interest runs on unpaid tax from the first day. MTD penalties, plainly has the detail.

You, or your accountant?

It depends on how straightforward your affairs are. Simple ones (one business, a bit of savings interest, no adjustments to make) are well within reach of doing it yourself. Anything with capital allowances, several income sources, losses or a joint property arrangement is where an accountant earns their fee, and the common pattern is that you file the quarters and they handle the year end. MTD if you have an accountant sets out that split.

What QuarterFile will do, and when

QuarterFile files quarterly updates, and filing opens for the 7 February 2027 quarter; the final declaration follows, in time for the first deadline on 31 January 2028. When it arrives it will be part of QuarterFile Free as well as Plus.

What it will do is carry your four quarters through, ask you for the parts that aren’t in them, and show you HMRC’s calculation before you declare anything. What it won’t do is make the judgement calls: where a cost is genuinely uncertain, or an adjustment needs deciding, that’s a conversation with your accountant.