How to submit your 2017-18 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.
Different ways to submit your tax return
Depending on how you choose to submit your tax return, the deadline for submitting it will be different.
Paper tax returns need to be filed by 31 October. So, for tax returns relating to the year 6 April 2017 to 5 April 2018, for example, all paper returns should be submitted by 31 October 2018.
The deadline for filing online is three months later – 31 January. So, tax returns for the year 6 April 2017 to 5 April 2018 can be filed online up to 31 January 2019.
Important tax deadlines for the 2017-18 tax year
31 July 2018 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 have to pay is based on your earnings for 2016-17, and if you pay less than what you've earned over 2017-18, a further 'balancing payment' will be due on 31 January 2019 - when you'll also have to make your first payment to cover the 2018-19 tax year.
31 October 2018 This is the deadline for filing a paper tax return, whether you choose to work out how much tax your owe yourself or want HMRC to do it. However, if you receive notice from HMRC that you must file a tax return after 31 July 2018, 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 - but don't be tempted to try and do both.
30 December 2018 If you file your tax return online and also have earnings taxed under PAYE, you can opt to have overdue tax (if it is less than £2,000) collected by PAYE, provided you filed your online return by this date. The advantage of this is that any tax payable would be paid over 12 months from April 2018, rather than in a single lump sum by 31 January 2019.
31 January 2019 This is the final deadline for online tax returns, unless the notice to make an online tax return is issued by HMRC after 31 October 2018, in which case you have three months from the date of issue. This is also the deadline to pay any tax due for paper and online filers.
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.
Find out more: If you need more help with tax, or any other aspect of your finances, sign up to a £1 trial with Which? and you can speak to a member of our Money Helpline team to get individual guidance.