October 31 marks the deadline for paper tax returns for 2016-17.

Last year 1.2m people filed a paper return. If you have not yet sent yours, you’ll need to post it special delivery tomorrow to ensure it reaches HM Revenue & Customs (HMRC) on Tuesday.

Do I need to file a return?
Even if you are an employee, you may need to complete a return if capital gains tax is due, if your earnings exceeded £100,000, or if you earn more than £50,000 and have to pay the child benefit tax charge.

The UK’s 4.85m self-employed people must also file a tax return.

Check and double-check
Before you put it in the post, make sure you have avoided the common errors highlighted by HMRC. These include failing to submit capital gains calculations where applicable, and only sending the sections for which you have entered data.

Have key paperwork to hand. This includes details of income and benefits such as private medical insurance — found in your P60 and P11D forms — any dividend payments and any deductible expenses.

What if I miss the deadline?
If you file a paper return after October 31, you will incur a £100 penalty. You can register to file online instead, in which case the deadline is January 31.

If you are new to doing an online return, leave enough time. After registering for an account at online.hmrc.gov.uk, you will receive an activation code in the post. This must be used within 28 days or it will expire and you will have to request a new one.