How do I start to complete a Self Assessment?

A simple guide to common tax problems

What do I need to know if I need to complete Self Assessment return?

Usually, the best option is to complete your Self Assessment online and to do so, the first step is to contact HMRC. This can take a little while to set up, so it is a good idea to do this in plenty of time and not leave it until the last minute. 

In most cases, you need to let HMRC know by the 5th of October after the end of the tax year that you need to complete a tax return, if HMRC hasn’t been in touch with you. So, if the tax year runs from 5th April 2021 to 6th April 2022, and you started earning money in November 2021 you need to contact HMRC by 5th October 2022 to tell them you need to complete a tax return.

Once you are set up with HMRC you then have until the 31st of October of the same year, 2022 in this example, to submit a paper tax return or 31st of January of the next year for an online tax return.

Use the records you have kept to complete the boxes on the Self Assessment tax return.  This will mean you need to

  • Add up all of the income you have received during the year from 6th April to 5th of April and enter this on the relevant part of the form
  • And, for property or self-employment income, you also need to add up all of the expenses that you have paid and enter this on the relevant part of the form

Remember – if you are a sub contractor, you need to complete the section on self-employment.  You need to include the total income you received, using the tax certificates as well as any other income for other work done and details of any expenses for this additional work.  Don’t forget to include the tax paid on the Self Assessment return.

What do I need to know if I owe tax to HMRC?

The tax bill from a self-assessment tax return is due by the 31st of January the year following the year in which you earned the income.  

You may also have instalments of tax to pay every 6 months.

If you are struggling to pay your tax, you should contact HMRC to ask if you can arrange a ‘time to pay agreement’. This means that HMRC could accept you making monthly payments towards your tax rather than one big lump sum HMRC will ask you details about your income and household expenses when working out how much you can pay per month.

What happens if I  miss a deadline?

HMRC will automatically charge penalties if the deadlines are missed. These can get larger the longer past the deadline you get. You can appeal penalties if you have a ‘reasonable excuse’, but it can be hard to win an appeal.  HMRC will take into account problems related to Covid-19.

HMRC will also charge interest and surcharges if you are late paying tax. In most cases, it is not possible to appeal these charges.