How to File Your Self Assessment Tax Return
Complete guide to completing and submitting your personal Self Assessment tax return online with HMRC.
What You'll Need
- UTR (Unique Taxpayer Reference)
- Government Gateway login
- P60 from employers
- Dividend vouchers
- Bank interest certificates
- Pension contribution records
Step-by-Step Guide
Register for Self Assessment if needed
If this is your first return, register with HMRC by 5 October following the tax year. You'll receive your UTR.
- •Directors receiving dividends must register
- •UTR takes 10 days to arrive by post
- •Keep UTR safe - you'll use it every year
Gather all income information
Collect P60 (salary), dividend vouchers, bank statements (interest), property income records, and any other income sources.
- •P60 from each employer
- •Dividend vouchers from your company
- •P11D if you received benefits
Log in to HMRC online
Go to the HMRC website and log in to your personal tax account using Government Gateway credentials.
- •Different from business Gateway
- •Can start and save return
- •Return pre-populated with PAYE info
Complete employment income section
Enter salary, tax paid, and any benefits from your P60 and P11D. HMRC may have pre-filled some information.
- •Check pre-filled figures are correct
- •Include all employments
- •Add expenses if claiming them
Complete dividends section
Enter total dividends received from UK companies. Remember the £500 dividend allowance is tax-free.
- •Report gross dividend amount
- •No tax deducted at source
- •Foreign dividends reported separately
Complete other income sections
Add any other income: bank interest, rental income, capital gains, foreign income, etc. Only complete relevant sections.
- •Most bank interest reported automatically
- •Rental income needs own section
- •Capital gains over annual exemption
Claim any tax reliefs
Enter pension contributions (for additional relief), Gift Aid donations, and any other tax reliefs you're entitled to.
- •Basic rate pension relief already given
- •Higher/additional rate needs claiming
- •Marriage allowance if applicable
Review and submit
Check all figures, review the tax calculation, and submit the return. You'll see immediately what tax you owe.
- •Double-check all numbers
- •Print calculation for records
- •Deadline is 31 January
Pay any tax due
Pay by 31 January following the tax year. Can pay online, by bank transfer, or set up a budget payment plan.
- •Same deadline as filing
- •Payments on account may apply
- •Late payment triggers interest
Common Mistakes to Avoid
Missing the 31 January deadline
Forgetting to report dividends
Not claiming higher rate pension relief
Not budgeting for payments on account
Frequently Asked Questions
When is the Self Assessment deadline?
The online filing deadline is 31 January following the end of the tax year. For the 2024/25 tax year (ending 5 April 2025), you must file online by 31 January 2026. Paper returns have an earlier deadline of 31 October. Payment is also due by 31 January.
Do company directors need to file Self Assessment?
Yes, most company directors need to file a Self Assessment return, especially if they receive dividends or have income over £100,000. HMRC will issue a notice to file if they believe you owe tax. Even if all your tax is collected through PAYE, a return may still be required.
What happens if I miss the Self Assessment deadline?
An automatic £100 penalty applies if you are even one day late. After 3 months, daily penalties of £10 per day begin (up to 90 days). After 6 months, a further 5% of the tax due is added. Interest accrues on all outstanding amounts from the deadline date.
Can I file my Self Assessment return myself?
Yes, you can file your own Self Assessment return through HMRC's online portal. You will need your UTR number, National Insurance number, details of all income sources, and records of any expenses or reliefs you are claiming. The process typically takes 1-3 hours.
What payments on account do I need to make?
If your Self Assessment tax bill is over £1,000, HMRC requires payments on account. These are two advance payments, each 50% of your previous year's tax bill, due on 31 January and 31 July. You can apply to reduce payments on account if your income has dropped.
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