Do You Need to File a Self Assessment? A Simple UK Guide

If you're on PAYE and your tax affairs are straightforward, you probably don't need to file a Self Assessment. But "straightforward" covers fewer people than you'd think. Freelance on the side? Earn over £100k? Rent out a property? You're likely in scope.

Every year, thousands of people either file unnecessarily or miss the deadline because they didn't realise they needed to. Both are avoidable.

Who has to file?

HMRC uses Self Assessment to collect tax that isn't automatically deducted through PAYE. You'll normally need to file if, during the last tax year, you:

• Were self-employed and earned more than £1,000 (before expenses)
• Had total income over £100,000
• Received more than £2,500 in untaxed income (rental income, for example)
• Earned over £10,000 from savings or investments
• Claimed Child Benefit while earning above £50,000
• Were a company director (unless unpaid for a non-profit)
• Had foreign income on which UK tax is due
• Owed Capital Gains Tax on asset sales

Not sure? Use HMRC's online checker. It takes two minutes.

Common situations

Freelancing or side income

Any self-employed income above £1,000/year means you need to file. That includes freelancing alongside a full-time job.

Say you earn £40,000 from your employer and another £6,000 from freelance web design. Your employer handles tax on the £40,000 through PAYE, but you're responsible for reporting and paying tax on the £6,000 through Self Assessment.

Rental income

If your rental income exceeds £2,500 after allowable expenses, you must file. Between £1,000 and £2,500, contact HMRC directly as they may be able to collect it through your tax code instead.

Earning over £100,000

Everyone earning above £100,000 must file, regardless of income source. This is also where your personal allowance starts tapering: you lose £1 of allowance for every £2 earned over £100,000, and it disappears entirely at £125,140.

Savings and investment income

If your pre-tax interest from savings and investments exceeds £10,000, you need to file. Below that, tax is usually handled through your personal savings allowance and tax code adjustments.

How to file

Step 1: Register

If it's your first time, register with HMRC for Self Assessment. You'll receive a Unique Taxpayer Reference (UTR), which can take a couple of weeks.

Register at gov.uk/register-for-self-assessment.

Step 2: Gather your records

Before you sit down to fill it in, collect:

• P60 and/or P45 from employers
• Bank statements showing interest earned
• Invoices and records of self-employed income
• Receipts for allowable expenses
• Details of any property income
• Records of asset sales (for Capital Gains Tax)

Step 3: Complete and submit

Log in through your Government Gateway account and work through the return. HMRC's online system calculates your tax as you go, so you'll see what you owe before submitting.

Step 4: Pay what you owe

Payment is due by 31 January following the end of the tax year. For the 2024/25 tax year, that means 31 January 2026.

Deadlines and penalties

Deadline	Date
Register with HMRC	5 October after the tax year ends
Paper return	31 October
Online return	31 January
Payment due	31 January

Miss the filing deadline and you're looking at:

• £100 fine immediately, even if you owe nothing
• £10/day after three months (up to £900)
• Further penalties at six and twelve months, which can be a percentage of the tax owed

The simplest way to avoid penalties: file early. You can submit your return from 6 April onwards. Filing in May doesn't mean you pay earlier. Payment is still due on 31 January.

Payments on account

If your last Self Assessment bill was over £1,000, HMRC will ask you to make "payments on account": two advance payments towards next year's bill.

• First payment: 31 January (alongside your current year's bill)
• Second payment: 31 July

Each payment is half of last year's bill. If your income drops, you can apply to reduce them.

Claiming tax relief through Self Assessment

Even if you're not required to file, you might want to voluntarily if you're claiming:

• Pension relief on contributions above what your employer handles
• Gift Aid on charitable donations (higher-rate taxpayers can reclaim the difference)
• Professional expenses over £2,500 that aren't reimbursed by your employer

When you don't need to file

If all your income is taxed through PAYE and you have no other income sources, you almost certainly don't need to. HMRC will tell you if they think you should file; you'll receive a notice to do so.

If you've been filing but your circumstances have changed (say you stopped freelancing), you can ask HMRC to withdraw you from Self Assessment.

Useful links

• Check if you need to file: gov.uk/check-if-you-need-tax-return
• Self Assessment deadlines: gov.uk/self-assessment-tax-returns/deadlines
• Allowable expenses for the self-employed: gov.uk/expenses-if-youre-self-employed
• See how your salary breaks down: salary calculator