Do I need to complete a tax return?

Updated on 6 April 2017

This section looks at what a tax return is and whether or not you need to complete one.

If you are in ‘self assessment’, you must complete a tax return (SA100) each year, on which you need to show your income and capital gains, and claim allowances and reliefs. We explain how this might apply to you.

What is self assessment (SA)?

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 complete a self assessment tax return, you include all your taxable income, and any capital gains. You also claim any tax allowances or reliefs that you are entitled to on the tax return.

You send the form to HMRC either on paper or online. The information on the tax return is used to calculate your tax liability. This process is called self assessment.

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Do I need to complete a self assessment tax return?

Most people in the UK pay all their tax ‘at source’, for example, through Pay As You Earn (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 one or more of the following apply to you:

  • You are working for yourself – you are self-employed;
  • You are a partner in a partnership business;
  • You are a company director, except for directors of not-for-profit organisations who receive no pay;
  • You are a minister of religion – any faith or denomination;
  • You are a trustee or the executor of an estate.

You also might need to complete a self assessment tax return if:

  • You have untaxed income. This could be, for example, interest that is not taxed before it is paid to you or rental income. If you are an employee or a pensioner and the income is less than £2,500 a year you might not have to complete a tax return. But if you receive other untaxed income and the tax due on it cannot be collected via your PAYE coding notice you will need to complete a tax return;
  • You receive regular annual income from a trust or settlement, or you receive income from the estate of a deceased person and further tax is due;
  • You have taxable foreign income whether or not you are resident in the UK. This includes non-UK resident landlords. You can find out more on the GOV.UK website;
  • You have income from savings and investments of £10,000 or more before tax;
  • You have annual income of £100,000 or more before tax;
  • You or your partner receive child benefit and your income is over £50,000. This is because of the high income child benefit charge;
  • You have tax due at the end of the year that cannot be collected via your PAYE coding notice in a later year;
  • Your untaxed income is £2,500 or more – but if you are a pensioner you may be able to pay your tax through your PAYE Coding Notice;
  • Your claims for expenses are £2,500 or more;
  • You have capital gains where:
    • You have given away or sold assets worth £45,200 or more for 2017/18; or
    • You have a capital loss but your gains net of any losses are more than the annual exemption for 2017/18 of £11,300; or
    • You have no losses to claim but your gains are more than the annual exemption for 2017/18 of £11,300; or
    • You need to make any other capital gains tax claim or election for the year.

HMRC may also want you to complete a return for other reasons.

Note that if HMRC have sent you a tax return or a notice to complete one, then you must fill it in and return it by the due date unless there is a good reason you do not need to be in self assessment and HMRC agree to cancel it. See below – What do I do if I no longer need to complete a tax return?

For more information on any of the above please have a look at the GOV.UK website. There is also a tool on GOV.UK to help you understand if you need to do a tax return.

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What are the important deadlines and dates for self assessment?

When we talk about dates for tax, often the date is said to be ‘during the tax year’ or ‘following the end of the tax year’. A UK tax year runs from 6 April to the following 5 April.

So when we talk about the tax year 2017/2018 it starts on 6 April 2017 and finishes on 5 April 2018. The 31 January during the tax year is 31 January 2018, the 5 October following the end of the tax year is 5 October 2018 and the 31 January following the end of the tax year is 31 January 2019.

Not all of the dates listed below may apply to you. You can follow the links that give you more information to help you decide if you need to take some action by that date.

31 January (during the tax year)


If you have to make payments on account, the first payment on account for the tax year ending the following 5 April is due. 

For example, the first payment on account for the 2017/18 tax year is due by 31 January 2018.

Not everyone has to pay these payments on account.

April (after the end of the tax year)  

The tax year ends on 5 April and shortly after this date anyone who is required to file a tax return will receive a notice advising that you must file a tax return for the tax year just ended.

31 July (following the end of the tax year)  

If you have to make payments on account, the second payment on account for the tax year ending the previous 5 April is due.

For example, the second payment on account for the 2017/18 tax year is due by 31 July 2018.

Not everyone has to make  Not everyone has to pay these payments on account.

5 October (following the end of the tax year)


If you did not submit a tax return for the previous tax year, but you need to submit one for the tax year that ended on 5 April, you must notify HMRC by 5 October. This might be to tell HMRC that you have income that has not been taxed before you received it or capital gains in excess of £11,300 (2017/18). This is so that HMRC can send you a tax return. 

Find out more on GOV.UK.

31 October (following the end of the tax year)


If you are sending HMRC a paper tax return this must be submitted by the 31 October. If you send the form after this date there will be a penalty even if you have no tax to pay.

30 December (following the end of the tax year)


If you file your tax return online, you will need to submit it by this date if you want HMRC to collect the tax through your tax code. This may be possible where you owe less than £3,000. If your income is more than £30,000, even more tax may be collected through your tax code.

31 January (following the end of the tax year)


All tax returns filed online must be submitted on this date. If you miss this deadline a penalty will be charged even if you have no tax to pay or have already paid all of the tax you owe.

Your balancing payment of tax is due at this time. For example your balancing payment for 2017/18 is due on 31 January 2019.

You may also have a payment on account to make at this time. For example you may have a payment on account to pay for the 2018/19 tax year on 31 January 2019.

Not everyone has to make payments on account.

31 January (following the end of the tax year ) + 1 year

If you become aware that an entry on your paper or online tax return is incorrect you can amend that return up to 12 months after 31 January following the end of the tax year.

For example, if you need to amend your 2016/17 return you have until 31 January 2019 to make the amendment. This applies whether you filed manually using a paper return or completed it online.


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What records do I need to keep?

There is a legal requirement for people in self assessment to keep records. If HMRC check your tax return, they may ask to see some of your records.

You can keep records on paper or digitally.

HMRC can charge you a penalty if your records are not complete and accurate.

In self assessment but not self-employed

If you submit your tax return on time, you should keep your records for at least 22 months after the end of the tax year. For example, you should keep records for your 2015/16 tax return until at least 31 January 2018.

If you submit your tax return late, you should keep your records for at least 15 months after you sent your tax return.

There is more information on record-keeping for self assessment on GOV.UK.

Self employed

The normal rule for the self-employed and those letting property is to keep business records for at least six years.

For more information on the records that you must keep visit our page ‘business records’. There is also more information on the GOV.UK website.

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What do I do if I no longer need to complete a tax return?

If your circumstances have changed and you think you no longer need to complete a tax return, for example, because you pay all your tax under PAYE, let HMRC know as soon as possible. You can contact HMRC using the details on the GOV.UK website.

If you have already received a tax return for a year, HMRC might agree to cancel it, if you explain your circumstances to them over the telephone. If they agree to withdraw the return, you will no longer need to submit it and any penalties for missing the filing deadline will be set aside.

If HMRC do not agree, however, they may ask you to complete the return and to tell them about the change in your circumstances in the Additional Information boxes.

They might also agree to cancel the tax return, but instead issue you with a ‘simple assessment’, if they think you have not paid enough tax.

If you have not received a return for the year but think you might receive one, contact HMRC and let them know why you think you no longer need to complete a self assessment return – you might be in time to stop them issuing one.

If you normally file a tax return, any refund that you are due is automatically calculated as part of the tax return process. However, if you are no longer within self assessment, but still think you are due a refund, you may need to claim a repayment of tax each year. If you think this applies to you, take a look at the ‘How do I claim tax back?’ page in the ’tax basics section’ of this website.

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What if I have not completed a tax return previously?

Notification deadline

If you have not received a tax return but you had income or capital gains on the list above you need to notify HMRC by 5 October following the end of the tax year in which you had the income, or you may face a penalty. HMRC will then send you a tax return to complete.

There is information on how to register for self assessment on GOV.UK.

It is worth noting that if you notify HMRC after 5 October, provided you have paid your income tax liability in full by the usual 31 January payment deadline, HMRC may reduce the late-notification penalty to zero. Note in these circumstances that you should also make sure you file your tax return on time (see below). You can find out more on our penalties page.

Submission deadlines

If you have to file a self assessment tax return, you normally have:

  • until 31 October to do so, if you choose to submit a paper tax return;
  • or until the following 31 January if you file online.

This means you have an additional three months for online filing compared with paper.

HMRC take the date of the first return received by them and this also triggers any late filing penalty. So if, for example, you file a paper return for 2016/17 after 31 October 2017, you cannot avoid a late filing penalty by filing the return online before 31 January 2018.

When you first register for self assessment, you may need to consider the following submission deadlines too:

  • If you want HMRC to calculate your tax –
    • If HMRC issue you with a tax return before 31 August, you have until 31 October to submit it on paper;
    • If HMRC send you a tax return to complete on or after 1 September, you have two months from the date of issue to complete and submit the paper form;
  • If you are happy to calculate your own tax liability (if you submit online, the software will automatically calculate the tax due) –
    • If HMRC ask you to submit a tax return before 31 July, you must submit the return on or before 31 October (paper) or on or before 31 January (online);
    • If HMRC ask you to submit a self assessment tax return after 31 July but by 31 October, you must submit the return within three months of the date of the notice (for paper returns) or on or before 31 January (for online returns);
    • If HMRC ask you to submit a self assessment tax return after 31 October, you must submit the return (whether paper return or electronic) within the three months beginning with the date of the notice.

Examples

Alfie 1 – not completed return previously – new sources of income

Alfie notified HMRC that he would need to complete a 2016/17 tax return on 17 September 2017. HMRC issued a return on 1 October 2017. Alfie needs to send the form to HMRC by 1 December 2017, that is, within two months of the date of issue of the return, if he wants HMRC to calculate his tax liability for him.

Alfie 2 – submission date for return – calculating own tax

If Alfie is asked to send in a self assessment tax return after 31 July 2017 but before 31 October 2017 – let us say 1 September 2017 – he will have a period of three months beginning with the date of the notice to get the form to HMRC – so by 1 December 2017 if he is using a paper return or on or before 31 January 2018 if he is filing online.

If Alfie is sent a self assessment tax return after 31 October – the return, whether paper return or online filing, must be sent to HMRC within three months from the date of issue of the return. So if he gets the return on 1 December 2017 he must send it in before 1 March 2018.

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What is a short tax return?

If you receive self assessment returns and file on paper rather than online but have simple tax affairs, you may be able to receive the short tax return instead of the full self assessment tax return. For example, this might apply if, as an employee you are in receipt of employment income, self-employment profits and your turnover was below £83,000 (2016/17), and you have straightforward investment income, or a reasonably small amount of income from property.

The short tax return is four pages long and so is around one-third the size of an average self assessment tax return with supplementary pages. The guidance is also much shorter and simpler. There is no need to calculate the tax on the form, but there is a two page simple calculation to give you a rough idea of your tax liability.

Filing dates are the same as for the full self assessment return.

The short tax return is normally issued automatically based on the information in the previous year's return. However, you need to tell HMRC if your circumstances change. There is a list of who is able to use the short tax return at the front of the guide notes, so that you can see if you still qualify.

You cannot download the short tax return. You can only use the short tax return if HMRC ask you to. If you are not issued with an actual tax return but instead you are sent a notice requiring you to complete a tax return, you can request that a short tax return be issued to you, if appropriate.

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Where can I find more information?

You can find more information on self assessment in the ‘self-employment section’ of this website.

There is more information on who needs to complete a self assessment tax return on the GOV.UK website.

There is more information on how to reclaim tax if you do not need to complete a tax return in the section ‘how do I claim tax back?

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