PAYE vs Self Assessment: how UK income tax actually gets paid

Last updated: 5 May 2026

TL;DR

PAYE collects income tax and National Insurance from employment and pension income at source, every pay period, via your tax code. Self Assessment is an annual reconciliation system for income that PAYE cannot capture - self-employment, rental, dividends, capital gains and certain higher-rate situations. Many people are in both.

In one sentence

PAYE is the at-source system run through your payslip; Self Assessment is the year-end reconciliation system run through a tax return.

What is PAYE?

PAYE - Pay As You Earn - is the UK's at-source tax-collection system for employment and pension income. Your employer or pension provider applies an HMRC-issued tax code to each pay run, deducts income tax and National Insurance, and remits both to HMRC. The deduction is visible on your payslip, and HMRC reconciles it against an annual figure on your P60 at the end of the tax year. For most employees with a single job, PAYE is the beginning and the end of their tax administration.

PAYE works through a few moving parts: your tax code (which encodes your tax-free allowance), the basis on which it is applied (cumulative or week 1 / month 1), and the bands and thresholds HMRC publishes each year. For 2026/27, the personal allowance appears to remain £12,570 and the rUK basic / higher / additional rates 20% / 40% / 45%.

What is Self Assessment?

Self Assessment is HMRC's annual self-reporting system. You file a tax return that declares income from sources PAYE cannot see directly: self-employment profits, rental income, dividends and savings interest above the allowances, capital gains, foreign income, and certain higher-rate adjustments such as additional pension relief. HMRC then calculates the tax due and you settle any balance - or claim a refund - through the return.

Self Assessment runs on a tax-year basis (6 April to 5 April) and has fixed filing and payment deadlines: paper returns by 31 October following the year-end, online returns and balancing payment by 31 January, and payments on account due 31 January and 31 July where applicable. HMRC publishes the criteria for who must file on gov.uk; the "Check if you need to send a Self Assessment tax return" tool is the authoritative reference.

Side-by-side comparison

Dimension	PAYE	Self Assessment
Who runs it	Your employer or pension provider, on HMRC's behalf	You (the taxpayer), reporting to HMRC
Frequency	Every pay period (weekly / monthly)	Once per tax year
Document	Payslip + P60 + P45	SA100 tax return
Income covered	Employment, occupational pension, some state pension	Self-employment, rental, dividends, savings, gains, foreign income
National Insurance	Class 1 deducted at source	Class 2 / Class 4 calculated through the return
Filing deadline	n/a (operated by employer)	31 January (online) following tax year end
Payment deadline	Same as pay date	31 January balancing + 31 July payment on account
Late penalties	Employer-side (RTI submissions)	£100 immediate, plus daily and tax-geared penalties
Higher-rate pension relief	Partially via tax code	Reconciled fully through the return
Refunds	Adjusted via tax code or P800	Direct to bank via the return
Used by most people?	Yes	A minority - but a growing one

Want to sense-check whether your PAYE deductions look right before any Self Assessment kicks in? Run a free payslip check.

When you might be in PAYE only

A typical PAYE-only taxpayer is an employee with one job, no significant savings income, no dividend income above £500 (the 2026/27 allowance), no rental income, and earnings below the £100,000 threshold where the personal allowance starts to taper. For this profile, the payslip and the year-end P60 are normally all the documentation HMRC needs. Errors tend to be tax-code mismatches rather than missing income - see our wrong-tax-code checklist if your code looks off.

When you might be in Self Assessment too

You usually need to file Self Assessment if any of the following applies during a tax year (the gov.uk "check if you need to send a return" page is the definitive list):

Self-employed (sole trader) with trading income above the trading allowance.
Director of a limited company whose tax position cannot be settled through PAYE.
Rental income above the property allowance.
Untaxed savings or dividend income above the personal savings / dividend allowances.
Capital gains above the annual exempt amount.
Income over £150,000 (criterion has shifted recently - check gov.uk).
Claiming higher-rate pension relief or Gift Aid above what PAYE handles.
Foreign income or non-domiciled circumstances.

Where the two systems interact

PAYE and Self Assessment are not alternatives - they are two parts of the same plumbing. If you have an employed job and a side hustle, PAYE collects tax on the employment salary each pay period, while Self Assessment reconciles the side-hustle profit and any higher-rate adjustments at year end. HMRC may also use PAYE to collect a Self Assessment liability under £3,000 by adjusting your tax code - the so-called PAYE underpayment route - rather than asking for a separate payment.

That is also why your tax code can change mid-year. If HMRC discovers untaxed income via the Self Assessment process (or a P11D), it may reissue a code for the next year that reduces your allowance to claw the tax back through PAYE. You can model the effect using our income-tax calculator.

Pros and cons of each

PAYE

Pros: automatic, low-effort, no annual filing, immediate visibility on the payslip. Errors are usually small and surfacable through a payslip check.

Cons: blunt tool for higher-rate pension relief, multiple jobs, or non-employment income; mid-year code changes can confuse; the system relies on HMRC having current data about your circumstances.

Self Assessment

Pros: precise reconciliation, full control over claims and reliefs, proper handling of side income. The right tool for a complex picture.

Cons: annual filing burden, fixed deadlines, payment-on-account cash-flow impact, and stiff penalties for late filing or payment. Errors can be costly without professional help.

How to know which applies to you

The most reliable route is gov.uk's "Check if you need to send a Self Assessment tax return" tool, which walks through HMRC's criteria. If you only have a single PAYE job and no other income, you are almost certainly PAYE-only. If anything in the list above applies, expect to be in both.

Frequently asked questions

Can I be in both PAYE and Self Assessment?

Yes, and many people are. Common combinations include an employed person with rental income, a self-employed sole trader who also has a part-time PAYE job, or a higher-rate taxpayer who needs to reconcile pension relief. PAYE handles the employment income; Self Assessment reconciles the rest.

Do I always need to file a tax return if I am self-employed?

Generally yes if your trading income exceeds the trading allowance (currently £1,000) and you are a sole trader. HMRC publishes the criteria - gov.uk's 'Check if you need to send a Self Assessment tax return' tool is the authoritative guide.

Why might HMRC ask a PAYE-only earner to file Self Assessment?

Higher-income reasons include earnings over £150,000, untaxed savings or dividend income above the allowances, capital gains over the annual allowance, or claiming higher-rate pension or charity relief. The criteria are listed on gov.uk.

Does Self Assessment replace my payslip?

No. If you are also employed, your employer still operates PAYE and issues a payslip each pay period. Self Assessment reconciles the picture across all sources at year end.

Educational content based on HMRC guidance for 2026/27. Not regulated tax advice. The authoritative source for whether you need Self Assessment is gov.uk.

Sense-check the PAYE side first - it is the easy half to verify.

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