How to File Your Final Declaration

The final declaration is the last step in your MTD tax year. It replaces the traditional Self Assessment tax return. You're confirming that your quarterly figures are complete and accurate, reviewing your tax calculation from HMRC, and formally declaring your income for the year. The deadline is 31 January following the end of the tax year — the same date as the old Self Assessment deadline.

Before you can file

To submit your final declaration, you need to have:

1. Submitted all four quarterly updates for the tax year. If any quarter is outstanding, you'll need to submit it first.
2. Claimed any annual adjustments (optional). If you have capital allowances, loss relief, or other annual adjustments to claim, do this before the final declaration. You can still file the declaration without adjustments — they're only relevant if you have claims to make.

Step-by-step: filing your final declaration

1. Navigate to the final declaration

From your dashboard, select the tax year and click Final Declaration. AffordableMTD checks that all quarterly obligations are fulfilled before allowing you to proceed.

2. Review your tax calculation

HMRC generates a tax calculation based on everything you've submitted — quarterly updates plus any annual adjustments. You'll see a summary that includes:

• Total income across all businesses
• Total allowable expenses
• Taxable profit after deductions
• Income Tax liability
• Class 2 and Class 4 National Insurance
• Total amount due

Check these figures carefully. If anything looks wrong, go back and correct your quarterly updates or annual adjustments before proceeding — once the final declaration is submitted, corrections require contact with HMRC.

3. Confirm the declaration

You'll see a declaration statement confirming that the information you've provided is correct and complete. Tick the checkbox to confirm.

4. Submit to HMRC

Click Submit Final Declaration. AffordableMTD sends the declaration to HMRC. You'll receive a confirmation screen with a submission timestamp and reference.

5. Pay your tax

The final declaration tells you how much tax you owe. Payment is due by 31 January. You pay HMRC directly — AffordableMTD handles the filing, not the payment. You can pay via your HMRC online account using bank transfer, debit card, or direct debit.

What if I need to make a correction after filing?

Unlike quarterly updates (which you can resubmit freely), the final declaration is a one-time formal submission. If you need to correct your figures after filing:

• Before the deadline (31 January): You may be able to amend through HMRC's online services or by contacting them. Check GOV.UK for the latest process.
• After the deadline: You'll need to contact HMRC to request an amendment. There are time limits on amendments (typically 12 months from the filing deadline).

This is why it's important to review your figures carefully before submitting. If in doubt, check with your accountant first.

Key deadlines

For the 2026-27 tax year (the first MTD year):

• Tax year ends: 5 April 2027
• Final declaration deadline: 31 January 2028
• Payment deadline: 31 January 2028

Frequently asked questions

Does the final declaration replace Self Assessment entirely?

For income covered by MTD (self-employment and property income), yes. However, if you have other income sources that need to be declared (like foreign income or capital gains), HMRC may still require additional reporting. Check GOV.UK for your specific circumstances.

Can my accountant file the final declaration for me?

Yes. If your accountant uses agent software, they can submit the final declaration on your behalf through their own MTD-compatible system.

What happens if I miss the deadline?

Late filing penalties apply. HMRC's new points-based system means you'll receive penalty points that can lead to financial penalties. Late payment also incurs interest charges. See our penalties guide for full details.