How Self Assessment used to work
Under Self Assessment, you'd spend the year keeping records — often informally — and then sit down once a year to complete your tax return. You'd log in to HMRC's website, enter your income and expenses for the full year, claim any reliefs, and get a tax bill. The online deadline was 31 January.
It was a once-a-year reckoning. Many people left it until January and spent a frantic few weeks digging out bank statements and receipts from the previous April.
How MTD changes the process
MTD for Income Tax breaks your filing into smaller, more frequent steps throughout the year — with the Final Declaration replacing the annual tax return at the end.
The process for each tax year looks like this:
- Four quarterly updates — You submit a summary of your business income and expenses four times a year (deadlines: 5 August, 5 November, 5 February, 5 May). These are not a tax calculation. They're simply a record of what you earned and spent each quarter.
- End of Period Statement (EOPS) — After your final quarterly update, you confirm and finalise your business figures. This is where you can make accounting adjustments — such as capital allowances if you're on the accruals basis. Most sole traders using cash basis will find this a straightforward confirmation step.
- Final Declaration — You confirm your total income for the year, including any non-business income, claim personal reliefs, and submit your finalised return. HMRC calculates your tax bill.
Key difference: Your quarterly updates are not a tax return and they don't produce a tax bill. They're an ongoing record. The Final Declaration is the moment you confirm everything and your tax liability is calculated.
What the Final Declaration includes
The Final Declaration brings together your complete tax picture for the year:
- Your business income and expenses — carried forward from your quarterly updates and EOPS, confirmed as final
- Other income sources — savings interest, dividends, rental income, employment income, pension income
- Personal allowances and reliefs — your personal allowance (£12,570 for 2026/27), Gift Aid donations, pension contributions, Marriage Allowance, and any other reliefs you're entitled to claim
- Any accounting adjustments — capital allowances, overlap relief, or other end-of-year adjustments made at the EOPS stage
Once you submit, HMRC calculates your Income Tax and Class 4 National Insurance liability for the year. Your payment on account dates remain the same: 31 January and 31 July.
When is it due?
The Final Declaration deadline is 31 January following the end of the tax year — the same date as the old Self Assessment online filing deadline.
| Tax year | Final Declaration deadline |
|---|---|
| 2026/27 (6 Apr 2026 – 5 Apr 2027) | 31 January 2028 |
| 2027/28 (6 Apr 2027 – 5 Apr 2028) | 31 January 2029 |
The tax payment deadline is also 31 January — any balance of tax owed for the previous year must be paid by this date. This hasn't changed from Self Assessment.
How do you file it?
The Final Declaration must be submitted through HMRC-recognised MTD software — not directly through HMRC's website. This is the same software you use for your quarterly updates.
Your MTD software will pull together your quarterly data, prompt you to complete the EOPS, and then walk you through the Final Declaration — adding any other income sources and claiming reliefs before you submit.
What if you have other income sources?
MTD for Income Tax covers your self-employment income. If you also have other taxable income — for example from renting out a property, PAYE employment, dividends, or significant savings interest — you'll include these in your Final Declaration just as you would have done in a Self Assessment return.
From April 2027, landlords with rental income above the threshold will also be brought into MTD, meaning their property income will be reported through quarterly updates too. Until then, rental income is included as a figure in the Final Declaration.
MTD filing sorted from the start
Bart handles your quarterly updates automatically — so when it comes to the Final Declaration, your business figures are already confirmed and your records are clean. No last-minute scramble.
Try Bart freeFrequently asked questions
Do I still need to file a Self Assessment tax return under MTD?
Not for your self-employment income. Under MTD for Income Tax, the Final Declaration replaces the Self Assessment tax return for sole traders. You still report all your income — including non-business income like rent, savings interest, or dividends — through the Final Declaration process in your MTD software.
What is the deadline for the Final Declaration?
31 January following the end of the tax year — the same date as the old Self Assessment online filing deadline. For the 2026/27 tax year (ending 5 April 2027), the Final Declaration is due by 31 January 2028.
What happens if I miss the Final Declaration deadline?
Missing the deadline triggers an automatic £100 penalty, with further penalties if the return remains outstanding after 3, 6, and 12 months. Interest also accrues on any unpaid tax from 31 January.
What is the End of Period Statement?
The End of Period Statement (EOPS) is a step you complete after your fourth quarterly update. It lets you make accounting adjustments to your business income and expenses — such as capital allowances if you're on the accruals basis — before submitting the Final Declaration. For most sole traders using cash basis, the EOPS is a straightforward confirmation step.