Most employees working in the UK pay all their tax through the PAYE system and are not required to submit a tax return. You may, however, need to complete a tax return because your tax affairs are complicated in some way, for example by having a source of untaxed income, in addition to your employment income.
You can find more detailed information on Self Assessment and tax returns in our tax basics section.
What is Self Assessment?
Self Assessment is not a tax – it is a way of paying tax.
The idea of Self Assessment is that you are responsible for completing a tax return each year if you need to, and for paying any tax due for that tax year. It is your responsibility to tell HM Revenue & Customs (HMRC) if you think you need to complete a tax return.
If you have to complete a Self Assessment tax return, you must also include your employment income (and taxes paid) and any other income that you have on your Self Assessment tax return, not just the income that has caused you to be in Self Assessment, as it is a return of all of your taxable income and gains for the year.
You also claim any tax allowances or reliefs that you are entitled to on the tax return.
When would I need to complete a Self Assessment return?
Most people in the UK pay all their tax at source, for example, through PAYE if they are employed, and are not required to file a tax return. So Self Assessment does not affect everyone and you will normally only need to complete a form if your tax affairs are complicated in some way, or if you have untaxed income that cannot be taxed through your PAYE tax code.
Also, if HMRC send you a tax return to complete or, more likely, a notice requiring you to complete a tax return, then you must do so (unless it can be withdrawn). HMRC may send you a tax return to complete, where they want to collect an underpayment of tax that has arisen, for example.
Most underpayments are collected by amending the taxpayer's tax code but where this is not possible (for example because it would cause hardship or where the taxpayer is no longer employed) HMRC will ask for voluntary payment. Where voluntary payment is not made, HMRC will issue tax returns to collect the underpayment, as this is the only way in which they can legally enforce the debt.
There is more information on who needs to complete a tax return in the tax basics section.
What should I do if all my other taxable income is not included in my coding notice?
Your coding notice is used by your employer or pension payer (but not for the state pension) to deduct tax from the payments made to you. If you have other taxable income, including the state pension, that is not included in your coding notice you should advise HMRC who will either amend your coding notice or require you to complete a Self Assessment return.
What do I do if I no longer need to complete a Self Assessment return?
We explain what to do if you think you no longer need to complete a Self Assessment tax return in the tax basics section.
If you are no longer within Self Assessment, but you have allowances or reliefs to claim, you may need to claim a repayment of tax each year, outside of the Self Assessment system. If you think this applies to you, take a look at the How do I claim tax back? page.
What if I have not completed a tax return previously?
The onus in the UK is on you to tell HMRC if you need to complete a tax return. You must register for a tax return by 5 October following the end of the tax year in question, otherwise you could incur a penalty.
We explain more about the deadline by which you need to notify HMRC if you think you need to complete a tax return in the tax basics section.
We also explain the deadlines for submission of tax returns.
What is a short tax return?
We explain what a short tax return is and help you work out whether or not you might be able to request one instead of the full Self Assessment tax return in the tax basics section.
Where can I find more information?
For more information on Self Assessment see GOV.UK.
There is more information on who needs to complete a Self Assessment tax return on GOV.UK.
There is more information on how to reclaim tax if you do not need to complete a tax return in the tax basics section.
