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Self-assessment tax deadlines

Chris Torney / 29 December 2016 ( 18 January 2019 )

We list the self-assessment tax return deadlines you need to know.

A woman misses her tax return deadlines

If you need to submit an annual tax return, there are a number of significant dates and deadlines that you may need to be aware of. If you are late either in filing your return or paying the tax that you owe, you could face stiff financial penalties.

January 31

This is when you need to have filed your return and paid any outstanding tax for the financial year which ended on the previous April 5. So January 31, 2019 is the filing deadline for returns covering the 2017-18 tax year.

However, you need to bear in mind that this deadline only applies to returns that are filed electronically via the HM Revenue & Customs website.

Avoid a late tax return penalty

October 31

If you are filing a paper return that has been posted to you by HMRC, on the other hand, it has to be received by your tax office by the October 31 that follows the end of the relevant tax year – so the paper deadline is earlier than the electronic one.

Even if you are filing a paper return, you don’t need to settle your account and pay any outstanding tax until the following January 31 – the same as for people who file online.

Self assessment checklist

July 31

If HMRC expects you to incur tax bills in future – for example, if you are self-employed – it will probably ask you to pay some tax “on account”. This means that, instead of paying all of next year’s tax in one go on January 31, you have to pay half of the expected bill six months early – by July 31 – and then the remaining half by the end of the following January.

If you are asked to pay tax on account but don’t expect to have such a large bill in the next financial year, get in touch with your tax office and ask for the “on account” payment to be reduced.

Four key things to remember when you pay your tax return

October 5

If you have a new source of income that isn’t being taxed at source – for example, you’ve started renting out a property – you need to tell HMRC about it by the October 5 that follows the end of the relevant financial year.

Six taxes you can legally avoid

So if you started getting rental income in September 2018, you would have until October 5, 2019 to notify your tax office.

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There are some nasty penalties for people who miss their deadlines.

If you file a paper or electronic return late, you can be charged a £100 fine – this is imposed even if you don’t owe any tax.

If you’re three months late, HMRC can start to impose a daily £10 fine up to a maximum of £900. After six months, late filers face a further £300 penalty or 5% of the tax they owe – whichever is greater. And there is another £300 fine after 12 months.

If you owe tax, you can also be fined a percentage of your outstanding bill on top of these penalties.

Bear in mind that if you send a paper return in after October 31, you could be fined £100. But if you instead decide to file electronically, you have an extra three months in which to do so.

HMRC says it will waive fines for people who have a “reasonable excuse” for filing late. There is more information about appealing against a fine on this basis here.

And HMRC has received some weird and wonderful excuses for filing late that definitely don't meet the 'reasonable' criteria. 


Self assessment tax myths dispelled

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The opinions expressed are those of the author and are not held by Saga unless specifically stated.

The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.