GoForma's FAQs around Self Assessment Tax Returns

We created this guide to answer the majority of frequently asked questions around Self Assessment tax returns

What is a Self Assessment Tax Return?

A Self Assessment Tax Return is a system HMRC uses to collect Income Tax.

What period does it cover?

The Self Assessment Tax Return looks at the period running from the 6th of April to the following 5^th of April each year.

Do I need to file a Self Assessment Tax Return?

Generally, HMRC is looking to collect Income Tax where it hasn't already been deducted at source. This could be high earners (those earning a salary above £150,000), sole traders, limited company directors, etc.

If you are simply earning a salary through PAYE, you do not need to register for self assessment.

If you have external income such as dividends, rental incomes, capital gains or self employment income, you will most likely need to register for self assessment.

If you earn less than £1,000 a year from self employment and rental income, you do not need to register.

You will also need to register if you earn over £60k and receive child benefit allowance.

You can use HMRC's tool here to check if you need to send a return.

What if I don't need to file a Self Assessment Tax Return for one year?

If you have no taxable income, you can call HMRC to let them know you don't need to submit a return. Alternatively, another solution which might be more manageable is to file a short tax return.  

I need to complete a return. What do I do now? 

If this is your first tax return, you must register at GOV.UK. While it's a straightforward process, it's essential to register sooner rather than later because it can take up to 10 working days in the UK (21 if abroad) for the registration to arrive in the post. 

Visit the website: www.gov.uk/log-in-file-self-assessment-tax-return. Have some identification and critical information, such as your passport, National Insurance number and bank details. 

Once registered, you will be given your Unique Taxpayer Reference (UTR), which will make future tax returns far easier. Anyone who registered before already has their UTR, which they use for all their subsequent declarations. 

Of course, we can assist with both registration and submission, so if you are unsure, please get in touch.

What is the deadline for registration?

For financial year 2024/25 you should have registered by the 5^th of October 2025.

Do I need to register every year?

No. Once you register, you receive a UTR that can be used to submit every year.

What happens if my Capital Gains are within the tax free threshold. Do I need to submit these within my Self Assessment Tax Return?

You do not have to pay tax if your total taxable gains are under your Capital Gains Tax allowance.

You still need to report your gains in your tax return if both of the following apply:

• the total amount you sold the assets for was more than 4 times your allowance
• you’re registered for Self Assessment

For how many years shall I keep records for HMRC audit purposes?

You may need to keep your records for up to 6 years from the end of the reporting period.

If you’re self-employed, HMRC state that you must keep your records for at least 5 years after the 31^st January deadline of the relevant tax year.

If you are not self-employed and send your tax return before the deadline, you should keep your records for at least 22 months after the end of the tax year the return is for.

If you are not self-employed and submit your return late, you should keep your records for at least 15 months after the tax return is submitted.

What is the deadline for submitting a Self Assessment Tax Return?

31^st October – Last day to file paper tax returns

The 31st of January – Last day to file tax returns online

What is the deadline for paying any tax calculated within my Self Assessment Tax Return?

The 31st of January – Balancing payments and payments on account (more on these next)

The 31st of July – Second payment on account

What are payments on account?

Payments on account are advance payments towards your next tax bill. They're calculated on your previous year's tax bill and made up of two amounts, each worth 50% of the total.

Can I reduce my payments on account?

If you know your tax bill will be lower than your previous year, you can apply for your payments on account to be reduced.

You should be confident that your tax bill will be lower. HMRC can charge interest/penalties if your tax bill exceeds what was predicted and you've adjusted your payments.

What happens if I miss the deadline?

If your return is submitted after the 31^stJanuary deadline, you'll receive an instant £100 penalty for the late submission.

If you also haven't paid the tax due before the deadline, HMRC will look to charge 5% on the amount due.

A late return of 90 days or more incurs a £10 a day penalty on top of your outstanding bill for a maximum of £900 over 90 days.

After six months, it's a further £300 fine or 5% of the tax you owe – whichever is greater.

Suppose you haven't submitted your Self Assessment tax return within 12 months after the due date. In that case, another £300 or 5% of the tax you owe will be added to what you already owe.

Why is my P60/P45 needed for a self-assessment tax return?

Suppose you have been employed throughout a tax year. In that case, you should either receive a P60 (if you were employed at the end of the year) or a P45 (if your employment ended before the end of the tax year).

These documents are required as they show your gross income received from your employment and the tax deducted (where applicable).

Where do I find my Self-assessment Unique Tax Reference?

HMRC will automatically send you a personal UTR number when your register for Self Assessment.

It will then be shown on all correspondence from HMRC relating to this as a 10-digit number. You'll also be able to see your UTR in your personal tax account if you have one.

Sometimes it may just be called 'tax reference'.

What do I do if I can't find my UTR?

Call the Self Assessment helpline to request your UTR if you cannot find any documents from HMRC.

How do I make the payment for this return?

Suppose we have assisted with completing your return. In that case, we will always send you the needed details for paying the tax due to HMRC upon submitting the return on your behalf.

You can find every way to pay here.

What if I can't pay?

We recommend contacting HMRC as soon as possible.

Providing you get in touch with HMRC before the payment deadline, HMRC is often very understanding and can help build a plan around your personal circumstances using their time-to-pay service.

You can setup a Self Assessment payment plan (Time to Pay) using your Government Gateway account, if you:

• have filed your latest tax return
• owe less than £30,000
• are within 60 days of the payment deadline
• plan to pay your debt off within the next 12 months or less

If you cannot make your own Time to Pay Arrangement online

Call the Self Assessment helpline if you cannot make your own Time to Pay Arrangement online; for example, you owe more than £30,000 or need longer to pay.

Self Assessment Payment Helpline
Telephone: 0300 200 3822
Monday to Friday, 8 am to 6 pm (excluding public holidays)