How PAYE Works: A Complete Guide to Pay As You Earn in the UK (2026/27)

You earn £30,000. Your employer pays you £2,078 per month. Where did the other £422 go? Most people couldn't answer that question beyond “tax.” PAYE (Pay As You Earn) handles 31 million UK workers, yet the deduction sequence — which calculations happen in which order, why your April payslip often looks different, and why cumulative vs. Week 1 basis changes everything — is almost never explained. This guide walks through the actual steps your employer follows every pay period, with real numbers.

1. What Is PAYE?

PAYE stands for Pay As You Earn. It is the mechanism by which employers deduct Income Tax and National Insurance from your wages on behalf of HMRC. Instead of receiving your full salary and paying tax in one lump sum at the end of the year, deductions are spread across each pay period (weekly, fortnightly, four-weekly, or monthly) so you pay a proportionate amount of tax with each payday.

The system was introduced in 1944 and is designed so that by the end of the tax year (5 April), you have paid almost exactly the right amount of tax — no refund needed, no underpayment to chase.

2. The Key Players in PAYE

• HMRC — Sets your tax code, collects payments from your employer, and reconciles at year-end
• Your employer — Runs payroll, applies your tax code, calculates and deducts tax/NI, sends the money to HMRC
• You — Provide your P45 (or complete a Starter Checklist if you don't have one), check your payslips, and query any errors

3. How Your Tax Code Drives the Calculation

Your tax code tells your employer how much tax-free income you're entitled to. The standard code for 2026/27 is 1257L:

• 1257 = multiply by 10 to get your annual tax-free allowance (£12,570)
• L = standard letter suffix (adjusts automatically if thresholds change)

On a monthly payroll, your employer divides £12,570 by 12 = £1,047.50 tax-free per month. Only earnings above this amount are taxed. For a full breakdown of every code letter and its meaning, see our Tax Code Guide.

4. Step-by-Step: How Your Monthly Pay Is Calculated

Here is exactly what happens each month for someone earning £36,000 per year (£3,000/month gross) with tax code 1257L:

Step 1: Work Out Taxable Pay

Monthly gross pay: £3,000
Monthly tax-free allowance: £1,047.50
Taxable pay this month: £1,952.50

Step 2: Calculate Income Tax

All £1,952.50 falls within the Basic Rate band (20%):
Tax this month: £1,952.50 × 20% = £390.50

Note: If you live in Scotland, your tax code will begin with “S” and different income tax bands and rates apply. See our Scottish vs English Tax comparison for a full breakdown.

Step 3: Calculate National Insurance

The NI Primary Threshold for 2026/27 is £12,570/year (£1,048/month). Employee NI is 8% on earnings between the Primary Threshold and the Upper Earnings Limit (£4,189/month):
NI this month: (£3,000 − £1,048) × 8% = £156.16

Your employer also pays NI on your salary (currently 15% on earnings above the Secondary Threshold). These employer contributions don't reduce your take-home pay, but they do affect the total cost of employing you. See our guide to employer National Insurance changes for details on the latest rates.

Step 4: Apply Other Deductions

If applicable: pension contributions, student loan repayments, salary sacrifice deductions, attachment of earnings orders, etc.

Step 5: Calculate Net Pay

5. Cumulative vs Week 1/Month 1 Basis

There are two ways PAYE can calculate your tax:

• Cumulative basis (normal) — your employer tracks your total pay and total tax from 6 April onwards. Each month, they recalculate whether you've paid the right total amount for the year so far. This means if you were overpaid in one month (e.g. emergency tax), you get an automatic refund in subsequent months.
• Week 1/Month 1 basis (non-cumulative, shown as “X” or “W1/M1” on your tax code) — each pay period is treated in isolation with no reference to previous months. This is used as a temporary measure when HMRC doesn't have enough information to set a cumulative code (e.g. new starters without a P45).

6. Emergency Tax: What It Is & How to Fix It

Emergency tax is applied when your employer doesn't have a valid tax code for you — typically when you start a new job without a P45. The emergency codes for 2026/27 are:

How to fix it: Give your new employer your P45. If you don't have one, complete a Starter Checklist. HMRC usually sends the correct code within 2–4 weeks and your employer will refund any overpaid tax under the cumulative method. For a full breakdown of what each code letter and suffix means, see our guide to understanding your tax code. For worked examples showing exactly how much you overpay on each emergency code, see our emergency tax code guide.

7. What Your Employer Reports to HMRC

Under Real Time Information (RTI), your employer submits a Full Payment Submission (FPS) to HMRC every time they run payroll. This includes your gross pay, tax deducted, NI contributions, student loan deductions, and pension contributions. HMRC uses this data in real time to check your tax position, which is why your Personal Tax Account often shows your current employment details within days.

8. Year-End: P60 and Reconciliation

After 5 April each year, your employer gives you a P60 — a summary of your total pay and total deductions for the year. HMRC also runs an automatic reconciliation: comparing what you've paid against what you should have paid. If there's a discrepancy, you'll receive either:

• A P800 tax calculation showing you overpaid — you can claim your refund online
• A PA302 coding notice showing you underpaid — the amount is usually collected by adjusting next year's tax code

9. Common PAYE Problems & Solutions

10. PAYE vs Self Assessment: What's the Difference?

PAYE handles tax automatically through your employer. Self Assessment is for self-employed workers, higher earners with complex tax affairs, or anyone with income not covered by PAYE (rental income, dividends, capital gains). Some people use both — you can be on PAYE for employment income and also file a Self Assessment return for additional income. See our Self-Employed Guide for details.

Case Study: Liam, a Warehouse Supervisor in Sheffield on £31,000

Liam is a 26-year-old warehouse supervisor in Sheffield earning £31,000 per year. He recently started his first full-time role after several years of agency work. When he received his first payslip, the tax deduction was much higher than he expected — £486 instead of the roughly £310 he calculated using our PAYE tool.

The issue was his tax code. Because Liam's previous agency employer had not issued a P45 before his start date, his new employer placed him on an emergency tax code of 1257L M1. The “M1” suffix meant PAYE was calculating his tax on a month-one (non-cumulative) basis — read our emergency tax code guide for a full breakdown of how this works and what it costs. Treating each month independently rather than spreading his Personal Allowance cumulatively across the year.

Liam logged in to his Personal Tax Account on GOV.UK and submitted his P46 details, confirming this was his only job and he had no other income. Within three weeks, HMRC issued his employer with the correct cumulative code of 1257L. On his next payslip, the PAYE system automatically recalculated his year-to-date position, and Liam received a £352 in-year refund covering the overpaid tax from his first two months.

Liam also noticed a workplace pension deduction of £93 (3% auto-enrolment via net pay arrangement). Initially he thought this was reducing his take-home pay unfairly, but after modelling it in our calculator with the pension field set to 3% salary sacrifice, he saw that the employer contributed 5% on top, giving him a total of 8% going into his pension at a real cost to him of only 3%. He decided to keep the pension running and focus on getting his tax code resolved as the quicker win.

The Hidden Cost of PAYE Timing: Why Your First and Last Payslips Are Almost Always Wrong

There is a subtle but consequential timing problem baked into PAYE that catches millions of UK workers every year, and almost no other guide mentions it. The cumulative basis assumes you will earn the same amount each month for the full tax year. But in practice, very few people start a new job on 6 April or leave on 5 April — and this misalignment creates temporary distortions.

When you start mid-year: Suppose you begin a new £36,000 job in September 2026 (Month 6 of the tax year). Your employer must apply the cumulative 1257L code, which means HMRC expects you to have earned £18,000 already that year. If you were unemployed or earning less before, you have “banked” unused Personal Allowance from April to August — five months' worth (£5,237). Your September and October payslips may show almost no tax deducted because PAYE is catching up on allowance you didn't use earlier.

When you receive a bonus: If your employer pays a one-off £5,000 bonus in November alongside your regular £3,000 salary, PAYE treats the £8,000 payment as your normal monthly income for cumulative purposes. If you were on track for a £36,000 annual salary, PAYE momentarily projects your annual income at £96,000 (extrapolating the one large month). This triggers Higher Rate deductions. The system self-corrects in December when your pay drops back to £3,000 — but the temporary tax spike alarms many employees who do not understand why they lost 40% of their bonus.

The payroll month boundary trap: UK payroll runs on monthly periods (Month 1 = 6 April to 5 May, not calendar months). If you leave on 4 May, you are treated as having worked only Month 1. But if you leave on 6 May, you have entered Month 2, and HMRC allocates two months' worth of allowance. This single day difference can shift hundreds of pounds of tax liability between months. Leavers who time their exit date poorly may wait until P800 reconciliation for a refund — which frequently takes six to twelve months after the tax year ends.

Real Numbers: What £36,000 Actually Looks Like on a Payslip Each Month

To bring all this together, here is what a standard monthly payslip looks like under PAYE for someone earning £36,000 on tax code 1257L with 5% salary sacrifice pension and no student loan — the actual figures most payroll guides skip over:

The percentage of gross salary that actually reaches your bank account in this scenario is 78.7%. That means for every £100 James earns, £21.30 goes to tax, NI, and pension. This figure drops to roughly 66% for someone on £55,000 and to as low as 52% for someone caught in the 60% trap at £110,000. Plug your salary into our calculator to see exactly where your income sits on this spectrum.

Understanding how PAYE works puts you in control of checking your payslip is correct. Cross-check your deductions with our salary calculator to verify that your monthly figures match what you expect.

PAYE calculations depend on your employer's payroll cycle, the tax code HMRC assigns to you, and whether the cumulative or Week 1/Month 1 basis applies. Payroll software providers (Sage, Xero, BrightPay) run these calculations automatically, but rounding differences of £1–£2 per month between providers are common. If your payslip figure differs from this calculator by more than £5/month, check that your tax code, NI category letter, and pension scheme type match your employer's payroll settings.