Self Assessment vs PAYE: What Is the Difference?
Quick answer: PAYE is the system employers use to take Income Tax and National Insurance from your wages before you are paid. Self Assessment is the system you use to report and pay tax on income HMRC has not already taxed at source. Employees normally use PAYE only. People with untaxed income use both.
Many people fall into both systems without realising it, particularly employees who start a side business or let out a property. This article explains how each system works, who belongs in which, and what happens when you sit in both.
Quick Overview- PAYE (Pay As You Earn) is operated by your employer or pension provider, which deducts Income Tax and National Insurance each payday and reports the figures to HMRC under Real Time Information.
- Self Assessment is a reporting system, not a separate tax. You declare your income for the tax year, and the same Income Tax rates apply.
- Being paid through PAYE does not automatically exempt you from filing a tax return.
- The main Self Assessment dates are 5 October to register, 31 October for paper returns, and 31 January for online returns and payment.
- A late online return triggers an automatic £100 penalty even where no tax is owed.
- Making Tax Digital for Income Tax has been mandatory since 6 April 2026 for self-employed people and landlords with qualifying income over £50,000. Those affected keep digital records and send quarterly updates instead of filing the traditional annual return.
What is PAYE?
PAYE is the system HMRC uses to collect Income Tax and National Insurance from employment income and most pensions at the point of payment. Your employer calculates the deductions using the tax code HMRC issues, then reports the figures to HMRC on or before each payday.
Because your personal allowance is spread across the year, deductions should even out over twelve months. The paperwork will be familiar: a payslip each pay period, a P60 after the tax year ends, a P45 when you leave a job, and a P11D where you receive taxable benefits such as a company car.
For most employees, nothing further is required. Tax is settled as you earn, and HMRC usually corrects small underpayments or overpayments through a change to your tax code.
What is Self Assessment?
Self Assessment is the process for declaring taxable income that has not been taxed at source. You report your income and gains for the tax year, which runs from 6 April to 5 April, and HMRC calculates the tax due from the figures you submit.
Before filing for the first time, you must register with HMRC, receive a Unique Taxpayer Reference (UTR), and set up a Government Gateway account.
One feature catches people out. If your last Self Assessment bill was more than £1,000 and less than 80 per cent of your tax was collected at source, you will normally make payments on account towards the following year. These are two instalments, each equal to 50 per cent of the previous year’s liability, due on 31 January and 31 July.
The system has also changed. Making Tax Digital for Income Tax replaced the annual return for the first group of taxpayers on 6 April 2026. HMRC is phasing it in over three years, using the qualifying income reported on an earlier tax return to decide who joins and when:
| Qualifying income from self-employment and property | Assessed on your return for | Start date |
| Over £50,000 | 2024/25 | 6 April 2026 |
| Over £30,000 | 2025/26 | 6 April 2027 |
| Over £20,000 | 2026/27 | 6 April 2028 |
Qualifying income is gross income from self-employment and property letting. Employment income taxed under PAYE, dividends, savings interest and pensions do not count towards the threshold.
Self Assessment vs PAYE: comparison table
The practical differences come down to who reports, when tax is paid, and who carries the risk of getting it wrong.
| PAYE | Self Assessment | |
| Who it applies to | Employees and pension recipients | Sole traders, business partners, landlords, directors with untaxed income, some higher earners |
| Who reports to HMRC | Your employer or pension provider | You |
| When tax is paid | Every payday | After the tax year ends |
| How the amount is set | Automatically, via your tax code | From the figures you declare |
| Main deadline | None for you | 31 January (online) after the tax year ends |
| Registration required | No | Yes, and you need a UTR |
| Records you rely on | Payslips, P60, P45, P11D | Invoices, bank statements, expense receipts |
| Penalty risk | Low, as errors are usually fixed through the tax code | Automatic £100 penalty for late filing, even where no tax is due |
Do I need to file a Self Assessment tax return if I am on PAYE?
Possibly. Being on PAYE does not remove the obligation to file if you have income HMRC has not already taxed.
You will normally need to file if any of the following apply:
- Self-employment income above the £1,000 trading allowance
- Rental income above the relevant property reporting limits
- Dividend or savings income above the available allowances
- Capital gains that need reporting
- The High Income Child Benefit Charge applies and is not being collected through your tax code
- Untaxed foreign income
- HMRC has issued you with a notice to file
A notice to file is a legal obligation. You must submit the return even if you believe no tax is owed, otherwise penalties apply. HMRC’s free checking tool on GOV.UK confirms whether you fall within the criteria, and it is worth keeping a copy of the result.
Can you be on PAYE and Self Assessment at the same time?
Yes, and it is common. Employees running a side business, employed landlords, and company directors taking a salary alongside dividends all sit in both systems.
The mechanics are straightforward. Your employment income still goes on the tax return, the tax already deducted under PAYE is credited against your total liability, and you pay the difference.
Where the balance owed is under £3,000, you can often ask HMRC to collect it through your tax code instead of paying a lump sum. To use that option, submit your online return by 30 December rather than 31 January. Keep your P60 to hand when completing the return, since the employment pages need the exact figures.
Which system applies to you? A quick check
Answer three questions:
- Is all of your income paid through an employer or pension provider?
- Did you receive anything HMRC has not already taxed?
- Has HMRC written to you asking for a return?
If the answer to the first question is yes and the others are no, PAYE almost certainly covers you. Otherwise, check your position using HMRC’s online tool before assuming nothing is due.
Common mistakes to avoid
- Assuming PAYE covers everything when there is side income from freelancing, trading or rent
- Missing the 5 October registration deadline for a first return, which delays the UTR
- Overlooking payments on account, then facing a larger than expected January bill
- Ignoring a notice to file because no tax appears to be owed
- Assuming Self Assessment still applies after crossing the Making Tax Digital threshold
Conclusion
The difference is who reports and when. PAYE handles tax automatically at source, while Self Assessment puts the responsibility on you to declare untaxed income after the tax year ends. If any part of your income arrives untaxed, check your filing position early rather than in January, when penalties are already running.