Important tax deadlines for the 2019-20 tax year
31 July 2019: payment on account due
If you're self-employed and pay your tax through payment on account, 31 July marks the deadline for your second payment.
The amount you pay is an estimate, based on your earnings for 2017-18. If you still owe tax (for example, if you earned more in 2018-19), a further 'balancing payment' will be due on 31 January 2020 - this is when you'll also have to make your first payment to cover the 2019-20 tax year.
5 October 2019: register for self-assessment
If you have never submitted a self-assessment tax return before, you must register to do so by 5 October 2019 in order to submit for the 2018-19 tax year.
31 October 2019: paper tax returns due
This is the deadline for filing a paper tax return. However, if you receive notice from HMRC that you must file a tax return after 31 July 2019, you'll need to send back the completed form within three months of the date of issue on the notice.
If you miss the deadline for filing your paper tax return, don't be tempted to try and file it late. You still have time to complete an online tax return instead (these aren't due until 31 January) - but don't submit both.
30 December 2019: opt into PAYE
If you file your tax return online and also have earnings taxed under PAYE, you can opt to have overdue tax collected via PAYE.
However, to be eligible your tax bill must be less than £3,000 and you must file your online return by this date. The advantage of this is that any tax payable would be paid over 12 months from April 2020, rather than in a single lump sum by 31 January 2020.
31 January 2020: online tax returns due
This is the final deadline for online tax returns - HMRC must have received your tax return by midnight.
The only time this deadline may differ is if you receive notice to make an online tax return from HMRC after 31 October 2019, in which case you have three months from the date of issue.
The deadline to pay your tax bill is also 31 January.
Fines for late tax returns
It's important to be aware that filing your tax return late, or failing to pay the tax you owe on time, will probably mean you face extra penalty fees and interest charges.
We've outlined the kinds of charges you could face below for missing the tax return deadline.
If you're late paying the tax you owe, you could face a host of additional fees. Find out more in our guide on late tax returns and penalties for mistakes.
How to submit your 2018-19 tax return
If you've never submitted a tax return before, you'll need to register with HMRC. You can do this online.
Once you've registered, you can choose from two ways to submit your tax return. You can either send a paper tax return to HMRC or fill in an online tax return on the HMRC website.
Making your tax return online has numerous advantages, which you can read more about on the online tax returns page of this guide.
Alternatively, you can use the Which? tax calculator - it's easy to use, jargon-free and offers personalised tax tips. Plus, you can submit the form directly to HMRC. Our video explains how easy it is to do.