Don’t run the risk of a penalty for a late tax return.

Your online tax return must reach HMRC by midnight on January 31st
You’ll get a penalty if you need to send a tax return and you miss the deadline for submitting it or paying your bill.
You’ll pay a late filing penalty of £100 if your tax return is up to 3 months late. You’ll have to pay more if it’s later, or if you pay your tax bill late.
You’ll also be charged interest on late payments.