Overview
This guide provides key information about Income Tax Self-Assessment, including who needs to file, important deadlines, and what records you need to keep.
What is Income Tax Self-Assessment?
Income Tax Self-Assessment is the system HMRC uses to collect Income Tax. As an individual, you are responsible for completing and filing your own tax return. The return covers a 12-month period from April 6th to April 5th of the following year.
Who Needs to File a Self-Assessment Tax Return?
You must file a Self-Assessment tax return if you:
Work in a self-employed capacity.
Are a Company Director.
Are a Partner in a business partnership.
Have more than one source of income (e.g., employed PAYE work and self-employed locum work).
Important Deadlines
Action | Deadline |
Online Filing | January 31st |
Paper Filing | October 31st |
First Payment on Account | January 31st |
Second Payment on Account | July 31st |
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Note: These deadlines are for the tax year that ended on the preceding April 5th. For example, the online filing deadline for the 2024/25 tax year is January 31st, 2026.
Can I Deduct Expenses?
Yes, you can deduct any expenses that were incurred "wholly, exclusively and necessarily" for your business. This means the expenses must be directly related to your work and have not been reimbursed by an employer.
What are Payments on Account?
If your last tax bill was over £1,000, HMRC may ask you to make "payments on account." These are advance payments towards your next tax bill, split into two instalments, to help you spread the cost. Each payment is half of your previous year's tax bill and is due on January 31st and July 31st.
What Records Do I Need to Keep?
You must keep detailed records of all your income and work-related expenses for at least six years from the end of the relevant tax year. This includes:
Business income and expenses
P60 and P11D forms from any employment
Bank and building society interest statements
Details of any pension contributions
Troubleshooting
Late Filing Penalties: If you file your tax return after the deadline, you will be charged a £100 penalty, which will increase over time. Late payments also incur a daily interest charge.
Need more help? For specific advice, it's best to consult a professional accountant.