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Introduction to Self Assessment tax returns

For many people, income tax and national insurance payments are automatically deducted by their employer and paid to HMRC. For anyone with a business or income from other sources, they must report it to HMRC on a Self Assessment Tax Return.

Who needs to file a tax return

There are a number of reasons why someone needs to file a tax return. Common reason for needing to file a tax return is receiving dividends or savings income over £10,000.

Self Assessment can be complicated and there are many reasons why a return needs to be submitted. HMRCs online checker helps you if you are unsure if you or anyone in your company needs to file a return. 

Registering for Self Assessment

To register for self assessment you can use HMRCs online form or post them a completes SA1 form.

It can take HMRC up to 6 weeks to process an application. 

Unique Taxpayer Reference (UTR) 

Once you've registered for Self Assessment, HMRC will send you your Unique Taxpayer Reference number in the post. 

If you've completed a Self Assessment in the past, you can find it on previously filed tax returns, a Notice to complete a tax return or on a Statement of Account. 

The Self Assessment UTR is made up of ten digits (e.g. 12345 67890) and is different to a company UTR number.

Our tax return filing service

Shortly after the start of each tax year we'll get in contact about Self Assessment tax returns. If you'd like us to take care of your tax returns we'll need you to answer a few questions and provide us with some details. 

As we have a such large number of returns to prepare, to be fair to all of our clients we prepare them on a first come first served basis.

Our monthly accountancy subscriptions aim to be flexible yet include everything you need so you don't get any surprise bills from us. There are a few situations where we have to charge an additional, one off fee for Self Assessment that you can find out more about in this guide.

Important dates

The deadline for filing Self Assessment Tax Returns online and making payments is 31st January. We begin work on them as soon as the tax year starts on the 6th April and we recommend filing your tax return as early as possible so you can understand if you owe further tax or if you are due a refund.

Even if your tax return is filed as early as April, you don’t have to make the payment immediately unless it is overdue. 

The deadlines for paying Self Assessment taxes are:

  1. 31st January – for any tax you owe for the previous tax year (known as a balancing payment) and your first ‘Payment on account’

  2. 31st July – for your second ‘Payment on account’

We need your completed questionnaire and any additional information to complete your returns before 31st October. After this date an additional fee of £95+VAT applies per return.

Payments on account

Payments on account are advance payments towards the tax bill you will owe for that tax year. For more information on how to pay Self Assessment and Payments on account, take a look at this guide.

HMRC penalties for late filing

HMRC allow almost 10 months from the tax year end to file Self Assessment Tax Returns (not that we recommend leaving it that late!).

As soon the return is one day late, HMRC automatically issue their first penalty and continue with additional penalties until the return is filed.

Overdue byPenaltyNotes
1 day£100This applies even if there is no tax to pay or if the tax due has been paid but the return has not been filed
3 months£10 for each following dayUp to a 90 day maximum of £900. This is in addition to the fixed penalty above
6 months£300 or 5% of the tax due, whichever is the higherThis is in addition to the penalties above
12 months£300 or 5% of the tax due, whichever is the higherIn serious cases they may apply a penalty of up to 100% of the tax due