Completing and filing a return

Your Tax Return must normally be filed (completed and submitted to HM Revenue and Customs) by 31 October following the tax year end (5 April) if you file on paper, or by 31 January following the tax year end if you file on-line. So the 2019 Tax Return (for the tax year 2018-19) is due by 31st October 2019, if filed by paper, or by 31st January 2020, if filed on-line. You will be sent your Tax Return – or a notice to file on-line – about May after the end of the tax year.

If you register for self assessment late (within three months of the filing deadline or later), the deadline is extended to three months from the date of issue of the return. The revised due date will be shown on the Tax Return/notice to file that you are sent.

What happens if my tax return is late?

There are penalties for late payment of tax, late filing of tax returns and late notification of liability to pay tax.

Penalties for failing to notify liability to pay tax

If you have a new source of income on which there is a tax liability, you should notify HMRC by 5 October following the end of the tax year in which the income arose.

EgSusy inherits a flat and first rents it out in June 2018. This is in the tax year to 5 April 2019. So Susy must tell HMRC about the rental income by 5 October 2019 at the latest.

If HMRC is not notified in time ‘failure to notify’ penalties can apply. These are based on the tax due and unpaid at ‘due date’ – normally the 31 January following the end of the tax year. The size of these penalties depends on taxpayer behaviour.

Factsheet CC-FS11  contains information about the penalties HMRC may charge where there has been a failure to notify.

Penalties for late payment

  1. 5% of tax unpaid after 30 days
  2. Another 5% of tax unpaid after 6 months
  3. Another 5% of tax unpaid after 12 months

Penalties for late filing

  1. You will be charged a penalty, even if you do not owe any tax.
  2. If you miss the filing dates of  31 October following the end of the tax year (for paper returns) or 31 January next following (for on-line submission), you will be charged a penalty of £100, and this will not be refunded, even if no tax is owing. Eg. tax returns for the year to 5 April 2019, should be filed on paper by 31 October 2018, or on-line by 31 January 2019
  3. If you are three months late, you will be charged a daily penalty of £10 per day, up to a maximum of £900
  4. If you  are six months late there will be a penalty of £300 (or 5% of the tax owing if this is greater)
  5. If you are 12 months late, you will be charged another £300 (or 5% of the tax owing if this is greater). In exceptional circumstances a higher penalty of up to 100% of the tax due is possible


If you pay your tax late you will be charged interest.  You will also be charged interest on late payments on account (which are due on 31 January and 31 July).

Penalties for errors and mistakes on returns

You may be charged penalties if there are errors on your return.

Appealing against a penalty

If there are exceptional circumstances which explain why you missed the tax return filing deadline, you can appeal against the penalty.  You can download the usual appeal form SA370 from the website.

What if I have many years worth of tax returns to complete?

You may normally only submit three years worth of late tax returns. For example, in the tax year 2018-19 (ie from 6 April 2018 to 5 April 2019) you may submit returns for 2017/18, and three late returns – 2014/15, 2015/16 and 2016/17.

If  HMRC has raised estimated tax bills (called ‘determinations’), then you have only three years from the 31 January filing date within which to send in a return.

Once this deadline has passed, your only statutory recourse is ‘Special Relief’. Special Relief may be difficult to obtain unless there are exceptional reasons why you have missed the tax return deadlines and you have good evidence of your income.

What happens if I don’t send in my Tax Return?

If you are sent a tax return, you are legally obliged to fill it in and send it back, even if you don’t owe any tax (even if you have not earned any money for the year in question). The only exception is if you can persuade HMRC to withdraw the tax return (see above).

If you don’t sent the return back you will be charged penalties and might be sent an estimated tax bill (called a determination). Once a determination has been made HMRC  is entitled to the tax due as set out on that determination and  can collect it through the courts – even to bankruptcy. The only way to cancel the debt is to send in a tax return to establish the correct amount of tax due.