Self Assessment tax return SA100 forms

If you’re self employed, run a business or have income from other sources, then you may be required to complete an SA100 form.

Form SA100 is the official name for a UK self assessment tax return form. Millions of UK tax payers complete a self assessment tax return every year and it’s used to provide information on individuals income to HMRC, so HMRC can work out how much tax is owed.

In this blog we explain more about the SA100 self assessment tax return, the information required and how to complete and file the tax return.

What is an SA100 form?

Self assessment relates to the process you go through to submit information about your income to HMRC. The SA100 form is a multi-page form you are required to fill out to complete the self assessment tax process.

The SA100 form is used to report your income from all sources during a tax year, any capital gains you’ve made from the sale of items and to claim tax reliefs and any repayment due to you.

Depending on the complexity of your income, you may have to complete supplementary pages to provide HMRC with further information. These supplementary pages will go into much more detail around specific income sources or capital gains.

Who must complete an SA100?

Individuals must send in a tax return if any of the following apply in a tax year:

• you were self-employed as a ‘sole trader’ and earned more than £1,000 (before taking off anything you can claim tax relief on)
• you were a partner in a business partnership
• company directors who receive income from non-PAYE sources
• you had a total taxable income of more than £150,000
• you had to pay Capital Gains Tax when you sold or ‘disposed of’ something that increased in value
• you had to pay the High Income Child Benefit Charge
• non UK residents earning UK taxable income, for example UK property income

You may also need to send a tax return if you have any untaxed income, such as:

• money from renting out a property
• tips and commission
• income from savings, investments and dividends
• foreign income

Some people choose to fill out an SA100 form if they want to:

• claim some Income Tax reliefs
• prove you’re self-employed, for example to claim Tax-Free Childcare or Maternity Allowance
• pay voluntary National Insurance Contributions

You can use the tax return for:

• student loan repayments
• interest and dividends
• UK pensions and annuities
• paying into registered pension schemes
• charitable giving
• claiming Blind Person’s Allowances
• High Income Child Benefit Charge
• Marriage Allowance
• claiming a repayment

Just because you have to complete a tax return form, doesn’t mean you will have to pay tax.

How do I get my SA100 self assessment tax return form?

Registering for self assessment with HM Revenue and Customs (HMRC) is a crucial step for individuals and businesses in the UK who need to report their income HMRC and pay the appropriate taxes. There are two primary methods to register for self assessment: online and by post.

You also have a choice on how you submit your self assessment form - these are online or by paper tax return. Online is the easiest and quickest way to file your tax return with HMRC.

To register online for self assessment, you will need to do the following:

• 1. Create an online account with HMRC
• 2. Get your Unique Taxpayer Reference (UTR)
• 3. Set up a Government Gateway Account
• 4. Activate your account

To register by post you must:

• 1. Get form SA1 paper form from the HMRC website or call the HMRC helpline
• 2. Complete and submit form SA1
• 3. Receive your Unique Taxpayer Reference (UTR)

What information do I need to complete Form SA100?

Before you start, it’s recommended you pull together some necessary documentation such as:

If you’re self employed:

• Your profit or loss account or your business records
• your bank statements, building society passbooks
• dividend counterfoils or investment brokers’ schedules
• personal pension contributions certificates
• national insurance number

Other things you may require or if you’re an employee:

• Forms P60
• End of Year Certificate
• P11D
• Expenses or benefits or P45
• Details of employee leaving work
• Payslips or your P2
• PAYE Coding Notice

You’ll need the following information to be able to complete your main tax return:

• self-employed income
• employment income (if you’re also employed)
• dividend income
• interest and dividends from UK banks and building societies
• rental income
• UK property income
• trust income
• foreign income
• pensions contributions
• gift aid
• UK pensions, annuities and other state benefits received
• payments on account made to HMRC
• redundancy lump payment or unemployment benefit
• capital gains
• Other taxable income

Tax return deadlines and penalties

If you are completing a paper tax return for tax year 23/24, HMRC must receive it by 31 October 2024 (or 3 months after the date on your notice to complete a tax return if that’s later).

If you are completing your tax return form online for tax year 23/24, you must send it online by 31 January 2025 (or 3 months after the date on your notice to complete a tax return if that’s later).

If you want HMRC to use your tax code to collect any tax you owe through your wages or pension, you must file online by 30 December 2024.

The deadline for paying your tax bill, or any Class 2 National Insurance contributions (NICs), is 31 January 2025.

If HMRC do not receive your tax return by the deadlines, you’ll have to pay a £100 penalty – even if you do not owe any tax. Further penalties are charged if your return is more than 3, 6 and 12 months late.

Complete your Self Assessment SA100 online with dns accountants

Completing a tax return correctly, avoiding errors or penalties can be complex. Most individuals use an accountant such as dns accountants to help complete their tax return on their behalf. Here at dns accountants our experts complete and file thousands of tax returns every year, do we will ensure that your tax return information is correctly completed.

There are huge benefits to getting your tax return completed by dns, here’s just a few of them:

Save time

Our process is totally streamlined, fast and efficient and a lot easier than doing your own tax return.

Fixed price

Our tax return service is cheap and gives you excellent value for money, compared to doing your own.

Minimise tax

Our tax experts will ensure you don’t pay a penny more than you have to in tax. You’ll get 15 minutes with our tax specialists and receive our expenses guide to know what are allowable expenses.

Our leading tax return service gives you problem-free self assessment filing. We promise you:

• No penalty guarantee.
• Fixed fee, no surprises.
• Simple, painless process.
• Data validated and checked.
• All statutory requirements met.

For help and advice on your tax return forms call us on 03300 886 686 or email on enquiry@dnsaccountants.co.uk.

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About the author

Siddharth Agarwal
I am a Chartered Tax Advisor (OMB) and ACCA. I have 9+ years of experience in owner-managed business taxation issues, company reorganisations, property taxation, and succession planning. I also work with private clients on bespoke tax planning strategies for trusts, residence status, and non-residents. I aim to fulfil my professional duties towards my clients and keep them satisfied, my utmost priority. I believe in establishing and maintaining businesses and personal relationships as the key to mutual growth.