How to do a final declaration for Making Tax Digital (MTD)

If you use Making Tax Digital for Income Tax (MTD for Income Tax), the “final declaration” is the step where you finalise your year-end position and submit your tax return through compatible software.

In practice, many people will think of this as the end-of-year MTD tax return step. HMRC’s user guidance mainly refers to this as “submit your tax return”, while HMRC’s technical guidance uses the term “final declaration”. 

What is a final declaration in MTD?

Under MTD for Income Tax, you keep digital records and send quarterly updates during the year. At the end of the tax year, you then:

• review the full-year figures,

• make any year-end adjustments,

• add any other taxable income/gains that are not already included,

• check HMRC and software data,

• and submit your tax return (your final declaration) through your MTD-compatible software. 

HMRC says your information is only treated as final once you have submitted your tax return. 

Who needs to do this?

MTD for Income Tax starts being mandatory in phases. HMRC’s current guidance says that from 6 April 2026, sole traders and landlords must use it if their annual income from self-employment and property is over £50,000 (with later phases extending to lower thresholds). 

If you are in MTD for Income Tax, the final declaration is part of your annual compliance cycle.

Before you start your final declaration

Make sure you have completed the earlier MTD steps for the tax year:

1) Send all quarterly updates

You should have sent all required quarterly updates (including the fourth/final quarterly update for the tax year). HMRC’s adjustment guidance specifically starts from the point after your fourth quarterly update. 

2) Check your digital records are up to date

HMRC expects you to have been correcting your digital records during the year so they are accurate. 

3) Use compatible software

HMRC does not provide MTD software. You must use compatible software (or a combination of products, including bridging software if appropriate) that can handle records, quarterly updates, and tax return submission. 

Step-by-step: How to do your final declaration (MTD)

Step 1: Review your year-end totals in your software

After your fourth quarterly update, your software should show your self-employment and/or property income and expenses for the whole tax year for each business. 

This is your starting point for finalising your position.

Step 2: Make year-end adjustments

Before you finalise and submit, you may need to adjust the data already sent to HMRC. HMRC gives examples including:

• removing disallowable expenses (tax adjustments),

• prepayments/accruals (accounting adjustments),

• adjustments for non tax-year-aligned accounting periods,

• and claiming reliefs/allowances. 

HMRC also notes that most adjustments are made by changing annual category totals, rather than editing every individual transaction. 

Common examples of adjustments

• Private use adjustments (for example, a phone used partly personally)

• Prepayments/accruals if you use traditional accounting

• Capital allowances

• Rent a Room relief

• Trading allowance or property allowance (where eligible) 

Step 3: Add your other income sources and gains

Your final declaration is not just about your quarterly business/property updates. HMRC says you must make sure your other taxable income and gains are included in your MTD-compatible software. 

Information HMRC may add automatically

HMRC says it may add certain information it already holds, such as some PAYE income, pensions, student loan repayments and certain other items. 

Information you may still need to add yourself

HMRC gives examples such as:

• savings income,

• dividends (including from your own company),

• partnership profit share (as an individual partner),

• and other income/gains not automatically added. 

Step 4: Check all information carefully

Before submitting, check both:

• information you added, and

• information HMRC added. 

If something is wrong, HMRC says you can overwrite it with the correct information before submitting. 

This is the most important quality-control step because your submission becomes final only once you file the return. 

Step 5: Review the tax calculation in your software

HMRC says you need to:

• confirm you’re ready to submit,

• view the software calculation showing tax due,

• and check the calculation is correct. 

If your software cannot produce a calculation when requested, HMRC says that indicates an error and your software should explain next steps (or you should contact the software provider). 

Step 6: Make the declaration and submit through software

To complete the final declaration, you submit your tax return in your MTD-compatible software and declare that the information is correct and complete to the best of your knowledge. HMRC sets out this process in its “Submit your tax return” guidance. 

HMRC says your software should then confirm the tax return has been submitted. 

Deadline for the final declaration (tax return submission)

HMRC says you must submit your tax return by 31 January following the end of the relevant tax year, though you can submit earlier. For example, a return for the 2025 to 2026 tax year can be submitted after 6 April 2026 and must be filed by 31 January 2027. 

MTD for Income Tax does not change the normal Self Assessment payment dates. 

Can you amend a final declaration after submission?

Yes. HMRC’s MTD technical guidance says that once a customer has completed their final declaration through software, they generally have 12 months from the statutory filing date to make changes (subject to the relevant rules). 

HMRC’s developer guidance also gives an example that for the 2025 to 2026 tax year, customers have until 31 January 2028 to make changes. 

Common mistakes to avoid

Submitting before making year-end adjustments

Quarterly updates are not the same as your final tax position. HMRC expects adjustments and checks before final submission. 

Forgetting other income sources

You may still need to add savings, dividends or other income not automatically populated by HMRC. 

Using software that cannot submit the full return

HMRC notes that some software may not support all income sources, in which case you may need alternative/additional software. 

Leaving it too late

You can submit earlier than 31 January, which gives time to fix issues before the deadline. 

Quick checklist for your website readers

Before clicking “submit” in your MTD software, make sure you have:

• sent all quarterly updates for the tax year

• reviewed full-year income and expenses

• made tax/accounting adjustments

• claimed any reliefs/allowances you’re entitled to

• added other taxable income/gains

• checked HMRC-populated information

• reviewed the tax calculation

• declared the return is correct and complete

• submitted by 31 January deadline 

Suggested disclaimer for your page

This guide is for general information only and does not constitute tax advice. Making Tax Digital rules and HMRC guidance can change, and the correct treatment depends on your circumstances. If you’re unsure, check the latest HMRC guidance or speak to a qualified tax adviser.