How To Complete A Self Assessment Tax Return

Do you complete a tax return?

If your tax affairs are simple or if you are employed you may not need to ‘self assess’.  If you do have to calculate your own tax, however, read our handy guide to completing a self assessment tax return.

Paper vs Online

There are two ways that you can complete a self assessment tax return.  You can either do it online or by sending in a paper based tax return.

There are a several advantages to completing your tax return online:

  • The online system automatically calculates any tax payable
  • You will get an acknowledgement that HMRC have received your return (you do not receive a receipt if you submit a paper based tax return)
  • You have longer to file the return
  • Online returns are processed more quickly

If you want to complete a self assessment tax return online, you have to register on the HMRC website.

Fill in the right pages

When completing a tax return, the most important thing to remember is that you have to complete all the relevant pages.  This may include both the ‘core pages’ and a series of supplementary pages.

Examples of supplementary pages include details of capital gains, income from property or pension income.  If you plan to submit your tax return online, you simply have to select the supplementary pages that you need.  For paper based returns, most of the supplementary pages can be downloaded from the HMRC website.

You should make sure that you have all your records and documents prior to completing your tax return.  You will need to provide exact figures to HMRC either online or on your paper based tax return.

Avoid these common mistakes

Whether you are submitting a paper based or online tax return, try to avoid the following common errors:

  • If it is a paper based return, make sure you sign and date it
  • Make sure you complete all additional and supplementary pages
  • Don’t change the year on a blank tax return to use it for an alternative tax year

Meet the deadline

If you are completing a paper based tax return, you must send it to HMRC by either 3st October (or 3 months after the date of issue of the notice to complete a return – whichever is the later).

If you are submitting your tax return online, you get an extra three months.  You have to submit your tax return electronically by 31st January (or, again, 3 months after the date of issue of the notice to complete a tax return – whichever is the later).

There is an automatic £100 penalty if you miss this deadline.


  1. arnold wayne says:

    made redundant in may now going self employed will i lose my notice pay of 12 weeks

  2. louis reid says:

    can i clame for doctors £150-00 and the £100-00 thease i have to pay to get my leiceance

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