If you need to complete a Self Assessment tax return for the 2025/26 tax year, the main online filing deadline is 31 January 2027.
January might still feel some way off, but preparing early can make the process much easier. It gives you time to gather your records, understand what you owe and deal with any questions before the deadline approaches.
At Xpert Accounting, we help individuals, sole traders and business owners prepare and submit their Self Assessment tax returns accurately and on time.
What is the Self Assessment deadline?
For the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026, the deadline for submitting an online Self Assessment tax return is:
31 January 2027 at 11:59pm
Any tax due for the year will normally also need to be paid by 31 January 2027.
The deadline for paper tax returns was 31 October 2026, so anyone still needing to submit their return will generally need to do so online.
Why file your tax return early?
You do not need to wait until January to submit your return.
Filing earlier can give you more time to:
- check that your income and expenses have been recorded correctly
- identify any missing documents
- understand how much tax you need to pay
- budget for your tax bill
- correct any issues before the deadline
- avoid the pressure of leaving everything until January
Submitting your return early does not normally mean you have to pay your tax early. The payment deadline remains 31 January 2027.
What information might you need?
Exactly what you need will depend on your circumstances, but it may include:
- income from employment or self-employment
- invoices and business income records
- allowable business expenses
- bank interest
- dividend income
- pension information
- rental income
- details of other taxable income
- records of tax already paid
- your Unique Taxpayer Reference where applicable
Keeping organised records throughout the year can make completing your return significantly easier.
Don’t forget allowable expenses
If you’re self-employed, certain costs incurred wholly for your business may be deductible when calculating your taxable profit.
This could include qualifying costs relating to areas such as office expenses, business travel, staff, advertising, professional fees and business premises.
Not every cost is allowable, and expenses that have both personal and business use may need to be apportioned correctly.
Getting this right is important. Missing legitimate expenses could mean paying more tax than necessary, while claiming costs incorrectly can cause problems later.
What happens if your tax return is late?
HMRC can charge penalties for filing your Self Assessment tax return after the deadline.
The initial late-filing penalty can apply even if there is no tax to pay, with additional penalties possible when a return remains outstanding.
There may also be interest and penalties where tax is paid late.
For that reason, it is better to deal with your return early rather than wait until the final few days of January.
Need help with your Self Assessment?
Self Assessment can become complicated when you have several sources of income, business expenses, property income or other tax considerations.
Xpert Accounting can help with the preparation and submission of your return, review the information you provide and help ensure relevant income and allowable expenses are dealt with correctly.
We’re based in Preston and support individuals and businesses across the UK.
If you’d like help preparing your 2025/26 Self Assessment tax return, get in touch with Xpert Accounting before the January deadline.