HM Revenue and Customs (HMRC) must receive your tax return and any money you owe by the deadline.
Deadline for telling HMRC you need to complete a return:
You must tell HMRC by 5 October if you need to complete a tax return and have not sent one before.
Deadline for submitting a paper return:
If you’re doing a paper tax return, you must submit it by midnight 31 October 2023.
Deadline for submitting an online return:
If you’re doing an online tax return, you must submit it by midnight 31 January 2024.
Deadlines for paying tax you owe:
You need to pay the tax you owe by midnight 31 January 2024.
There’s usually a second payment deadline of 31 July if you make advance payments towards your bill (known as ‘payments on account’).
You’ll usually pay a penalty if you’re late. You can appeal against a penalty if you have a reasonable excuse.