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The final declaration

Your annual confirmation to HMRC. Everything from employment income to capital allowances, and when to file.

5 min read

Once the tax year ends on 5 April, you have until the following 31 January to submit a final declaration. This is the MTD equivalent of a Self Assessment return: it's where your full tax position for the year is confirmed.

For the first MTD year (2026-27), the final declaration is due 31 January 2028.

What it replaces

The final declaration replaces the Self Assessment tax return for people in MTD. If you've been doing Self Assessment for years, the final declaration will feel familiar, it's the same information, pre-filled from your quarterly updates.

What goes into the final declaration

Your quarterly updates cover your sole-trade and property income and expenses. The final declaration lets you add everything else and confirm the final numbers:

  1. Your self-employment and property totals for the year. These pull through from your quarterly updates. You review them, make any last adjustments (for example, private-use disallowances, capital allowances, stock valuations, accruals), and confirm.
  2. Other income that isn't in quarterly updates:
    • Employment income and tax paid (from P60/P45).
    • Pensions (state and private).
    • UK bank and building society interest.
    • UK dividends.
    • Foreign income (including foreign pensions, dividends, interest).
    • Capital gains, if applicable.
    • Other miscellaneous income.
  3. Reliefs and allowances:
    • Pension contributions (for higher-rate relief).
    • Gift Aid.
    • Marriage Allowance.
    • Charitable giving.
    • Trading or property allowance, if you've elected to use it.
    • Child Benefit (for the High Income Child Benefit Charge, if applicable).
    • Student loan and postgraduate loan repayments.
  4. Year-end adjustments to the sole-trade and property figures that weren't in quarterly updates:
    • Capital allowances (on vehicles, equipment).
    • Stock valuations.
    • Accruals and prepayments.
    • Private-use adjustments (e.g. home-office proportion of household bills).
    • Loss reliefs and brought-forward losses.

How the process works

  1. After 5 April, the final declaration becomes available in your software.
  2. Your software pulls through your year-end sole-trade and property totals from your quarterly submissions.
  3. You review each business, make any adjustments (capital allowances, private-use, stock valuation and so on). Good software guides you through prompts; an accountant would do this for you.
  4. You enter your other income and claim reliefs.
  5. Your software triggers a tax calculation with HMRC. You get back a full breakdown: income tax due, Class 2 and Class 4 National Insurance, student loan (if applicable), payments on account, and the final balance owed or overpaid.
  6. You review the calculation. If something looks wrong, you can usually re-trigger after making adjustments.
  7. Once you're happy, you submit the final declaration.

The calculation step is the part people used to dread with Self Assessment, the "what do I actually owe?" moment. MTD doesn't change the numbers, but it does show you the calculation before you commit, so there are no surprises on the submit button.

When you should do this

Any time between 6 April and 31 January. Most people do it somewhere between June (when you have P60s) and January.

Sensible rhythm:

  • June–August: early review to spot any year-end adjustments while things are fresh.
  • September–November: actual submission, if you have all your numbers.
  • January: latest-safe window, especially if any of your income depends on year-end statements (investment income, for instance).

Don't leave it to the last week of January. System strain, software support queues, and last-minute surprises are real every year.

Pay on 31 January

Tax and National Insurance for the year are due by 31 January (same as Self Assessment). So for 2026-27:

  • File final declaration on or before 31 January 2028.
  • Pay income tax, Class 2 NI, Class 4 NI, and any payments on account, on or before 31 January 2028.

You can submit early and pay closer to the deadline, filing doesn't take money from you.

What if I realise I made a mistake after submitting?

The final declaration is marked as "irreversible" in software (because submitting it tells HMRC "this is my final position for the year"). But the tax system isn't, you can still amend.

If you discover an error after submitting:

  • Within 12 months of the filing deadline, you can amend the declaration through the usual channels (your software or a separate amendment process). This is the standard amendment window.
  • Outside that window, you can make an overpayment relief claim (if you paid too much) or disclose the error to HMRC (if you paid too little). The sooner the better.

Don't panic: errors are normal, and HMRC's usual response is "fix it and pay what's owed", not a penalty, as long as you didn't deliberately mislead them.

How to think about it

The final declaration is less a new scary form and more a confirmation screen on the data your software already has. Most of the year's work is the quarterly updates; January is just reviewing and adding the bits (employment, investments, reliefs) that your sole-trade/property software doesn't know about.

If you used to dread Self Assessment, the MTD final declaration is genuinely easier for most people, because the core numbers are already in place.

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