What is Self Assessment and Who Does it Apply To?
Self Assessment is the UK system of declaring tax information to HMRC.
It applies to:
- Sole Traders and partners
- Company Directors who owe tax
- Landlords
- Anyone else who owes Income Tax
You will need to send HMRC a Self Assessment return each year – in other words a tax return. Self Assessment is just the name given to the process.
Submissions and Deadlines
You can either:
- Have an accountant do this (eg ourselves – we would love to be your accountant of choice)
- Do it yourself online (we’ve written a guide about this) – you will need to register with HMRC online services for this
- Do it by paper (you will need to request a paper return to complete)
The deadline is:
- 31 January after tax year for a online return (eg 31 January 2026 for the 2024-25 tax year)
- 31 October after tax year for a paper return (eg 31 October 2025 for the 2024-25 tax year)
Your Self Assessment needs to include details of:
- Business profits (use a self employment supplement)
- Jobs and employments (use an a employment supplement, one for each job)
- Rents (land and property supplement)
- Savings income (bank interest, dividends)
- Pension payments
- Capital Gains (Capital Gain supplement – not normally due on selling your own house even if you teach there occasionally)
From April 2020 Capital Gains on residential property sales, other than your own home if fully tax exempt, must be declared within 60 days of sale, not on the Self Assessment.
If you submit it online, or have an accountant assist you, the calculation of tax due (the “Self Assessment” aspect) will be done for you.
Read our guide to filing your own Self Assessment Return (the first part of this covers getting information ready for either handing over to an accountant, or for filing yourself, the second part is a guide to filing yourself).
From April 2026 many Self Employed taxpayers will move into Making Tax Digital for Income Tax which will change the mechanics of Self Assessment for these taxpayers, although the overarching principles and tax calculation don’t change.