Four quarterly updates don't finish your year under Making Tax Digital. After the fourth one you still send a final declaration, and that's where your tax bill gets worked out. For the 2026/27 tax year it's due by 31 January 2028, the same date the old tax return was due. In practice it is your tax return. It just goes in through your MTD software instead of HMRC's online form.

What the quarterly updates don't cover

A quarterly update is a running total of your business income and expenses since 6 April. That's all. No tax is charged when you send one, and HMRC isn't treating the figures as final.

Everything else about your year goes into the final declaration:

  • Wages from a PAYE job, using the figures on your P60
  • CIS deductions the contractors took off your pay
  • Pension contributions and Gift Aid
  • Student loan
  • Bank interest, dividends and any other income
  • Year-end adjustments to the business figures, like capital allowances on a van

The CIS one catches a lot of people in construction. Your quarterly updates show your gross pay. The 20% the contractor kept back only counts at the end, in the final declaration. If some of the monthly statements are missing, your refund comes out smaller or later than it should.

When is the final declaration due for 2026/27?

Here's the whole year:

  • 7 August 2026: first quarterly update (6 April to 5 July)
  • 7 November 2026: second update (up to 5 October)
  • 7 February 2027: third update (up to 5 January)
  • 7 May 2027: fourth update (up to 5 April)
  • 31 January 2028: final declaration, and the tax for 2026/27 is paid

You can send the final declaration as soon as the fourth update is in. You don't have to wait until January.

Watch out for 31 January 2027 as well. That's still an old-style tax return, for 2025/26, with a payment. So if you're already in MTD you've got two January deadlines in a row, for two different years. They're easy to mix up.

The first-year let-off HMRC has given covers late quarterly updates. It doesn't cover a late final declaration or late payment.

Does paying the tax change?

No. Payments on account carry on as before. If your bill is over £1,000 and less than 80% of it was taken off at source, you pay half of next year's estimate on 31 January and the other half on 31 July.

So 31 January 2028 is a big one. It's the balance for 2026/27 plus the first payment on account for 2027/28, on the same day.

Start the paperwork now

Most of what goes into the final declaration isn't in your bookkeeping software. It's in a drawer, or in your email. The P60 from your employer in May or June. The CIS statement each contractor sends you by the 19th of the month. The letter from your pension provider. So:

  • Make one folder for 2026/27, on your phone or on paper
  • Save every CIS statement as it arrives, not next January
  • Add the P60, any student loan letters and bank interest statements
  • Photograph anything on paper. The shoebox works right up until you can't find the March statement

If you'd rather not think about any of this, that's the part we do. We send the quarterly updates, you send us the CIS statements and the P60 as photos on WhatsApp, and we do the final declaration. Have a look at our Making Tax Digital page, bookkeeping and pricing, or get in touch and Alex or Anca will go through your year with you.

Sources: HMRC, Use Making Tax Digital for Income Tax, Understand your Self Assessment tax bill: payments on account and What you must do as a CIS subcontractor. Correct as at October 2026.