Self Assessment: Who Needs to File a Tax Return?

Q: How do I register for Self Assessment?

Register online at gov.uk/log-in-file-self-assessment-tax-return. You will receive your Unique Taxpayer Reference (UTR) by post within 10 working days. The registration deadline is 5 October following the end of the tax year in which you needed to file — for the 2024-25 tax year that means 5 October 2025.

Q: What happens if I miss the Self Assessment deadline?

Missing the 31 January online filing deadline triggers an automatic £100 penalty even if you owe no tax. After 3 months, an additional £10 per day applies (up to £900). After 6 months, a further 5% of the tax owed (or £300, whichever is greater). After 12 months, another 5% of tax owed. Late payment also attracts interest on the unpaid amount from 1 February.

Q: Do employed people need to file Self Assessment?

Most employed people do not need to file Self Assessment because their income tax and NI are collected through PAYE. However, you must file if you earn over £100,000, have significant untaxed income (dividends over £500, rental income over £2,500, or self-employment income over £1,000), claimed Child Benefit and either partner earns over £60,000, or have capital gains above the £3,000 annual exemption.

Most employed people never need to file a Self Assessment tax return — PAYE handles everything. But millions of people do need to file, and failing to register on time triggers automatic penalties even when you owe no extra tax.

A simplified Self Assessment decision flowchart — see the full list of triggers below.

Who Must File Self Assessment?

HMRC requires you to file a Self Assessment tax return if any of the following apply to you in the tax year:

Self-Employment and Business Income

You are self-employed with trading income above £1,000 (net of the trading allowance). If income is below £1,000 you may use the trading allowance and are exempt from filing.
You are a company director with income not fully taxed through PAYE (salary paid outside PAYE, or dividends).
You are a partner in a business partnership.

High Income

Your total income (from all sources) exceeds £100,000. Above this threshold your Personal Allowance tapers away at £1 for every £2 over £100,000, and this must be managed via Self Assessment.
You have income from abroad (foreign employment, overseas pension, foreign investments).

Property Income

Your gross rental income exceeds £2,500 per year after allowable expenses (or £10,000 before expenses). Below £2,500 net HMRC may collect via a tax code adjustment rather than requiring a return.

Investment Income

You receive dividends over £500 in a tax year (the current Dividend Allowance for 2025-26). Even as a basic rate taxpayer with no additional tax to pay, you must file if dividends exceed this threshold.
You have capital gains above the Annual Exemption of £3,000 for 2025-26 — from selling shares, property (other than your main home), or other assets.
Savings interest that exceeds your Personal Savings Allowance (£1,000 for basic rate, £500 for higher rate taxpayers) and has not been collected through PAYE.

Child Benefit

You (or your partner) receive Child Benefit and either of you has adjusted net income above £60,000. The High Income Child Benefit Tax Charge must be declared and paid through Self Assessment.

Other Triggers

You have untaxed income from tips, casual work, or commission not reported through PAYE.
You receive income from a trust or settlement.
You have overpaid tax and need to claim a refund HMRC cannot process automatically.
HMRC has sent you a notice to file a return — you must file even if you believe you do not owe any tax.

Key Deadlines for 2024-25 Tax Year

Deadline	What It Covers
5 October 2025	Register for Self Assessment if filing for the first time
31 October 2025	Deadline to file a paper tax return
31 January 2026	Deadline to file online and pay any tax owed
31 July 2026	Second Payment on Account (if applicable)

Penalties for Late Filing

HMRC applies automatic penalties for missing the 31 January online deadline, even if you owe no tax:

Day 1: £100 automatic penalty
After 3 months: £10 per day (up to 90 days = £900)
After 6 months: 5% of tax owed or £300 (whichever is greater)
After 12 months: A further 5% of tax owed or £300

Late payment of tax also attracts interest at the HMRC late payment rate (currently around 7.25%) from 1 February onwards.

What You Need to Complete a Return

UTR number — your 10-digit Unique Taxpayer Reference (sent by post when you register)
P60 or P45 — showing employment income and PAYE tax deducted
Records of all income — self-employment, rental, dividends, savings interest, capital proceeds
Receipts for allowable expenses — if claiming deductions against self-employment or rental income
Pension contribution records — to claim higher rate relief not applied at source
Gift Aid records — donation amounts if claiming higher rate gift aid relief

Frequently Asked Questions

How do I register for Self Assessment?

Go to gov.uk/log-in-file-self-assessment-tax-return and register. Your UTR arrives by post within 10 working days. Register by 5 October following the end of the relevant tax year — so by 5 October 2025 for the 2024-25 year.

What happens if I miss the Self Assessment deadline?

An automatic £100 penalty on day one, then £10/day after three months (up to £900), then 5% of tax owed after six months and again after twelve months. Interest accrues on unpaid tax from 1 February.

Do employed people need to file Self Assessment?

Usually not — PAYE handles tax automatically. But you must file if you earn over £100,000, have dividends above £500, rental income above £2,500, capital gains above £3,000, or claimed Child Benefit with household income above £60,000.