MTD Year-End Process: Final Declaration Explained

The final declaration is the fifth and most important MTD submission of the year. It replaces your Self Assessment tax return and confirms your full-year tax position. Here is everything you need to know.

What Is the Final Declaration?

The final declaration is a year-end submission that:

• Confirms your total income and expenses for the full tax year
• Includes any adjustments to quarterly figures
• Adds capital allowances, loss relief, and other year-end items
• Calculates your Income Tax and National Insurance liability
• Replaces the self-employment and property pages of your Self Assessment return

Think of it as the definitive version of your accounts, after the four quarterly updates have provided provisional figures throughout the year.

When Is It Due?

The final declaration for each tax year is due by 31 January following the end of the tax year. This is the same deadline as the old Self Assessment return:

• Tax year 2026/27 (April 2026 – April 2027): Final declaration due 31 January 2028
• Tax year 2027/28 (April 2027 – April 2028): Final declaration due 31 January 2029

What It Includes Beyond Quarterly Updates

Your quarterly updates are summaries of income and expenses by period. The final declaration adds:

Capital allowances. Claims for business equipment, vehicles, and other capital expenditure using the Annual Investment Allowance or writing down allowances.

Loss relief. If your business made a loss, you can claim to carry it forward against future profits or (in some cases) set it against other income.

Private use adjustments. Final adjustments for expenses with a personal element (such as a home office or vehicle used partly for personal journeys).

Pension contributions. Tax relief on personal pension contributions.

Other adjustments. Any corrections to quarterly figures, timing adjustments, and other year-end items.

Preparing for Your Final Declaration

Start preparing well before the 31 January deadline:

1. Review all quarterly submissions — check for any errors or omissions across the four quarters
2. Gather year-end information — capital allowance claims, pension contribution certificates, any other relevant documents
3. Review your tax calculation — your software will generate a draft tax calculation. Review it carefully.
4. Consult your accountant — if you use one, have them review the final declaration before submission
5. Submit and pay — submit the declaration and ensure any tax owed is paid by the same deadline

Accounted prepares your final declaration automatically based on your quarterly data, highlighting anything that needs your attention.

Common Year-End Adjustments

• Correcting a miscategorised expense from an earlier quarter
• Adding a capital allowance claim for equipment purchased during the year
• Adjusting the personal use percentage on mixed-use expenses
• Claiming loss relief
• Adding pension contribution relief

What Happens After Submission

Once your final declaration is submitted and accepted:

• HMRC calculates your final tax liability for the year
• Any difference between tax already paid (through payments on account) and your final liability becomes either a balance payable or a refund due
• Payment on account for the following year is calculated

Stop dreading your Self Assessment. Accounted tracks everything throughout the year so January is just a click, not a crisis. Try it free.