MTD Final Declaration Explained
What replaces the old Self Assessment return once you're in MTD for Income Tax.
What the Final Declaration actually is
Once you're in MTD for Income Tax, you no longer file one annual Self Assessment return. Instead, you send four quarterly updates through the year, then submit a Final Declaration afterwards that confirms everything and finalises your tax position.
How it differs from quarterly updates
- Quarterly updates are running totals of business income and expenses — no tax calculation, just reporting
- Final Declaration is where you confirm the full-year totals, add any other income (employment, dividends, savings, property outside MTD), claim reliefs and allowances, and finalise the tax you owe
Think of the quarterly updates as keeping HMRC updated in real time, and the Final Declaration as the equivalent of what the old Self Assessment return used to do in one go each January.
The deadline
The Final Declaration is due by the same 31 January deadline that applied to the old Self Assessment return, covering the tax year that ended the previous 5 April. Missing it triggers the same late filing penalty regime — an immediate £100 charge, rising with daily and percentage penalties the longer it's outstanding.
Worked example
Tom's quarterly updates for 2026/27 report a running total of £42,000 income and £9,000 expenses from his self-employment. At the Final Declaration stage, he adds £3,000 of savings interest and confirms his Personal Allowance and Marriage Allowance transfer, then submits by 31 January 2028 to finalise his tax bill for 2026/27.
What to check before you submit
- Make sure all four quarterly updates for the year have actually been submitted — the Final Declaration builds on them
- Add any income not covered by your quarterly MTD updates, such as employment income, dividends, or savings interest
- Check you've claimed relevant reliefs and allowances — these aren't automatically applied from your quarterly figures
Sources: GOV.UK — Making Tax Digital for Income Tax. This page is general guidance, not personalised tax advice.
Frequently asked questions
It replaces it — confirming your total income built up from quarterly updates plus any other income, and finalising your tax bill.
By the same 31 January deadline as the old Self Assessment return, for the previous tax year.
Not necessarily — the Final Declaration is where you make final adjustments, corrections, or add other income before confirming.
Yes, quarterly updates can generally be corrected in a later update or finalised at the Final Declaration stage.