What is the MTD ITSA Final Declaration?
The Final Declaration is the year-end submission that replaces the old Self Assessment tax return under MTD ITSA. After four quarterly updates have been submitted for the tax year, you submit the Final Declaration to confirm the accuracy of your quarterly data, add any income or adjustments not covered by quarterly updates, and confirm your final tax liability for the year.
Think of quarterly updates as building blocks — four provisional snapshots of your income and expenses. The Final Declaration is the completed picture where everything is confirmed, adjusted, and finalised. It is the MTD equivalent of the old January Self Assessment return.
When is the Final Declaration Due?
The Final Declaration is due by 31 January — the same date as the old Self Assessment return. For landlords and sole traders who join MTD ITSA from April 2026, their first Final Declaration will be due 31 January 2027, covering the 2026/27 tax year.
What Does the Final Declaration Contain?
1. Confirmation of Quarterly Update Data
Your four quarterly updates feed automatically into the Final Declaration. You review the aggregated totals from all four quarters and confirm they are accurate. Any errors identified at this stage can be corrected before submission.
2. Year-End Adjustments
- Capital allowances — annual investment allowance and writing down allowances on business equipment
- Replacement of domestic items relief — for landlords replacing furniture and appliances
- Private use adjustments — where an asset is used partly personally and partly for business
- Section 24 mortgage interest credit — the 20% tax credit for residential landlords
3. Other Income Sources
Quarterly updates only cover your property and self-employment income. The Final Declaration is where you add all other income that does not go through quarterly updates:
- PAYE employment income
- Pension income
- Bank and savings interest
- Dividend income
- Capital gains
- Foreign income
4. Reliefs and Allowances
- Personal allowance (automatically applied)
- Pension contributions (higher-rate relief claimed here)
- Gift Aid donations
- Marriage allowance transfers
- Blind person’s allowance if applicable
Final Declaration vs Old Self Assessment — Comparison
| Old Self Assessment Return | MTD ITSA Final Declaration |
|---|---|
| Contains all income from scratch | Quarterly update data pre-populated |
| All income entered in one sitting | Only additions and adjustments needed |
| Tax liability unknown until filing | Running estimate already close to final figure |
| Due 31 January | Due 31 January — same date |
| Payment due 31 January | Payment due 31 January — same date |
| Often stressful, time-consuming | Much quicker — most work done quarterly |
What Happens After the Final Declaration is Filed?
HMRC calculates your final tax liability and issues a tax calculation. If you owe tax, it is due by 31 January. If you have overpaid (for example, through payments on account), HMRC processes the repayment. The tax year is then fully closed.
Frequently Asked Questions
AccTek handles your Final Declaration
We prepare, review with you, and file your year-end declaration — no January stress, no surprises.