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How to Complete Your Self Assessment: A Guide
How to complete your Self Assessment
Self Assessment is how HMRC collects tax from people whose income has not already been fully taxed. This guide covers registration, income, expenses, deadlines and submitting your return.
What is Self Assessment?
Self Assessment is a system used by HM Revenue and Customs to collect Income Tax.
You may need to complete a Self Assessment tax return if you are self-employed, receive rental income, have investment income or earn income that has not already been taxed at source.
The UK tax year normally runs from 6 April until 5 April the following year.
Who may need to complete Self Assessment?
Self-employed
People running their own business or earning income from freelance work.
Property income
People earning taxable income from renting out property.
Additional income
Income that has not already been taxed through PAYE or another source.
Partnerships
Partners who need to declare their share of partnership income.
Key Self Assessment terms
How to register for Self Assessment
Registration with HMRC is normally the first step if you need to complete Self Assessment.
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Register with HMRC
Create or access your Government Gateway account and register for Self Assessment.
Receive your UTR
HMRC will issue your Unique Taxpayer Reference after registration.
Keep the details safe
You will need your UTR when dealing with HMRC and completing your return.
Self Assessment deadlines
Paper Self Assessment returns normally need to reach HMRC by this date.
The normal deadline for submitting your Self Assessment online.
Late tax returns can lead to penalties and interest charges, so give yourself enough time to prepare.
What you need before completing your return
Preparing your documents before starting can make completing your return much easier.
Documents to have ready
- Your Unique Taxpayer Reference
- Your National Insurance number
- P60, P45 and P11D documents
- Business income records
- Receipts and allowable expenses
- Property income records
- Savings and investment statements
How to complete your Self Assessment
Gather your records
Collect details of income, expenses, investments and any other information relevant to the tax year.
Report your income
Enter the relevant income from employment, self-employment, property and investments.
Add your expenses
Include qualifying expenses and deductions that relate to your income or business activity.
Claim relevant reliefs
Include any allowances or tax reliefs you are entitled to claim.
Review and submit
Check the information carefully before submitting your return to HMRC.
What income might you need to report?
| Income type | Examples | Useful records |
|---|---|---|
| Employment | Salary and employment benefits | P60, P45 and P11D documents |
| Self-employment | Business and freelance income | Income and expense records |
| Property | Rental income | Rental statements and allowable costs |
| Investments | Interest and dividends | Statements from banks or investment providers |
Allowable expenses and tax reliefs
Depending on your circumstances, you may be able to reduce your taxable income by claiming qualifying expenses, allowances and reliefs.
Business expenses
Qualifying costs can include certain travel, equipment and business premises expenses.
Pension contributions
Some pension contributions may qualify for tax relief.
Gift Aid
Eligible charitable donations can potentially affect your tax position.
Tax allowances
You may qualify for allowances depending on your income and circumstances.
Keeping receipts, invoices and statements organised throughout the year can make your Self Assessment much easier to complete.
Paying your Self Assessment tax bill
HMRC provides several ways to pay your Self Assessment bill.
| Payment method | How it works |
|---|---|
| Bank transfer | Pay HMRC directly from your bank account using the correct payment reference. |
| Direct Debit | Set up a Direct Debit through HMRC where available. |
| Budget Payment Plan | Make regular payments towards your future Self Assessment bill. |
| Online payment | Pay using one of HMRC’s available online payment methods. |
Income from abroad or working overseas
Your Self Assessment can become more complicated if you are non-resident, work abroad or receive income from another country.
Where you live, where your income arises and your UK tax residence can all affect what needs to be reported.
Dealing with HMRC
HMRC may contact you by letter, email or through your online account. Make sure your contact information is kept up to date and read any communication carefully.
If you disagree with HMRC or believe something is incorrect, contact them as soon as possible. More complicated disputes may require professional tax advice.
Common Self Assessment mistakes
Give yourself enough time to prepare and submit your return.
Check your name, address, UTR and other details before submitting.
Keep receipts, invoices and financial records organised.
Put money aside rather than waiting until the payment deadline.
Make sure you consider allowances and reliefs relevant to your circumstances.
Self Assessment FAQs
What is the SA100 form?
Do I need to report self-employment income?
How is my tax calculated?
What happens if I miss the deadline?
Can an accountant complete my Self Assessment?
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