MTD Final Declaration Explained: What It Is and How to Submit It

Under Making Tax Digital for Income Tax (MTD ITSA), your annual tax return becomes a final declaration submitted through your accounting software. If you are used to filing a Self Assessment return each January, the process changes in substance but the deadline stays the same.

What Is the Final Declaration?

The final declaration is the year-end submission that confirms your complete income picture for the tax year. It replaces the traditional Self Assessment tax return for people within MTD ITSA.

By the time you reach the final declaration, you will have already submitted four quarterly updates covering your self-employment or property income and expenses. The final declaration is where you bring everything else together: other income sources, any end-of-year adjustments, reliefs, and allowances.

HMRC guidance confirms that once you submit the final declaration, the information generates your Self Assessment tax bill for that year.

How Is It Different from Quarterly Updates?

Quarterly updates contain your running income and expense totals for each quarter. They do not constitute your tax return. Think of them as progress reports. The final declaration is when you declare everything is complete and correct.

The key differences are:

• Quarterly updates cover only your self-employment or property income and expenses.
• The final declaration must include all other taxable income for the year.
• Quarterly updates do not trigger a final tax calculation. The final declaration does.
• Submitting the final declaration is the act of confirming accuracy and committing the figures to HMRC.

What Does the Final Declaration Include?

Before you submit, you will need to ensure all your income sources are accounted for in your software. Some information is added by HMRC automatically. Other information you add yourself.

What HMRC adds automatically

If HMRC already holds data about certain income sources, it will pre-populate your return. This includes:

• Employment (PAYE) income
• State, private, and occupational pension income
• Student loan repayments
• Construction Industry Scheme (CIS) subcontractor deductions
• Other taxable state benefits
• Capital Gains Tax residential property disposals
• Marriage Allowance claims

You should check anything HMRC has added before you submit. If something is incorrect, you can overwrite it in your software.

What you add yourself

You will need to enter any income that HMRC has not automatically included. This typically covers:

• Savings interest
• Dividends (including from your own company)
• Your share of profit from a partnership as an individual partner
• Any other miscellaneous income not pre-populated

End-of-year adjustments

After your fourth quarterly update, you may need to make adjustments before submitting the final declaration. These can include:

• Tax adjustments, such as removing disallowable expenses (for example, a proportion of personal phone costs)
• Accounting adjustments for prepayments or accruals if you use traditional accounting
• Capital allowance claims
• Rent a Room relief claims
• Trading or property income allowance claims

Your software will guide you through these. Most adjustments are made by updating annual category totals rather than individual transactions.

When Is the Final Declaration Due?

The deadline is 31 January following the end of the relevant tax year. This is the same date as the existing Self Assessment filing deadline.

For the 2026/27 tax year (starting 6 April 2026), the final declaration must be submitted by 31 January 2028. You can submit it earlier once the tax year has ended and you have all the information ready.

If you miss the deadline, HMRC's late submission penalty points system applies in the same way as for quarterly updates. Read our guide to MTD penalties and the points system for the detail on how penalties accumulate.

How Do You Submit the Final Declaration?

You submit through your MTD ITSA-compatible software. There is no separate HMRC portal for this. The steps are:

1. Complete your fourth quarterly update for the year.
2. Make any required end-of-year adjustments in your software.
3. Add any other income sources not pre-populated by HMRC.
4. Review the tax calculation your software generates.
5. Confirm the information is correct and complete.
6. Submit the final declaration through your software.

Your software will confirm the submission has been received. If you disagree with the calculation or find an error, you can correct the data in your software before submitting.

What Happens After You Submit?

HMRC uses the information to generate your Self Assessment tax bill. The payment deadlines do not change. Payments on account remain due on 31 January and 31 July. Any balancing payment is due by 31 January following the end of the tax year.

MTD ITSA does not alter when tax is paid, only how it is reported.

If you need to correct something after submitting, you can amend the return through your software.

Do You Still Need to Worry About Self Assessment?

In practice, the final declaration replaces the Self Assessment return for income covered by MTD ITSA. However, if you had a Self Assessment obligation for the tax year before you started using MTD, you still need to submit that year's return in the normal way first.

For most sole traders and landlords entering Phase 1 from 6 April 2026, this means filing a standard 2025/26 Self Assessment return by 31 January 2027, then switching to the MTD final declaration process for the 2026/27 year onwards.

What Software Do You Need?

Any HMRC-recognised MTD ITSA software must be capable of submitting the final declaration, not just quarterly updates. Before you choose software, check that it supports your specific income sources, including any non-trading income you need to declare. GOV.UK's software finder tool lets you filter by income type and accounting period.

Our MTD software and compliance guide has a summary of recognised options to help you compare.

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DigiTaxHub.co.uk is an independent information resource and is not affiliated with or endorsed by HMRC. This article is for information purposes only and does not constitute tax or financial advice. Always verify current rules at GOV.UK and speak to a qualified accountant if you are unsure.