What Is PAYE? How UK Pay As You Earn Tax Works (2025/26)

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PAYE is how most UK employees pay income tax without ever filing a return. This guide explains how PAYE deductions are calculated, what your tax code means, how Real Time Information reporting works, and what to do if you think you have paid too much or too little tax through the system.

What is PAYE and how does it work?

PAYE is the mechanism by which employers and pension providers deduct income tax and National Insurance from payments before they reach the employee. Rather than paying a lump sum once a year, tax is spread evenly across each pay period, so by the end of the tax year the correct total has usually been collected automatically.

The system relies on your tax code to spread the £12,570 Personal Allowance across the year. On a monthly salary, roughly £1,047 is treated as tax-free each month, with tax applied to the rest at the relevant band. Because the calculation is cumulative, an early-year correction can rebalance the whole year.

How do I read my tax code?

A standard 2025/26 tax code is 1257L: the number is your tax-free allowance divided by ten (£12,570), and the letter describes your situation. L means you get the standard allowance; BR means all income is taxed at the basic rate (common for second jobs); K codes mean deductions exceed your allowance, often due to taxable benefits.

Checking your code matters because HMRC issues it based on the information it holds, which may be out of date. A wrong code is the single biggest cause of PAYE errors. You can view and correct your code through your Personal Tax Account on GOV.UK.

What is Real Time Information (RTI) reporting?

Since 2013, employers must report PAYE to HMRC every time they run payroll, not annually. This Real Time Information system means HMRC sees your earnings and deductions as they happen, which feeds directly into Universal Credit calculations and lets the agency spot under-collection during the year rather than after it.

For employers, RTI compliance is a payroll obligation with penalties for late or inaccurate Full Payment Submissions. For employees, it means your tax position is far more current than it used to be, and refunds or corrections can be triggered mid-year.

How do I claim back overpaid PAYE tax?

If you overpay through PAYE — common after leaving a job mid-year, having the wrong code, or working only part of the year — HMRC often issues an automatic refund through a P800 calculation after the tax year ends. You can also claim directly through your Personal Tax Account rather than waiting.

Underpayments are usually collected by adjusting your tax code in a later year, spreading the cost. If you have multiple income sources, the safest approach is to reconcile your total income against the bands yourself, because PAYE handles one employment cleanly but can misallocate allowances across several.

What is the difference between PAYE and Self Assessment?

PAYE collects tax automatically from wages and pensions as you earn, while Self Assessment is a once-a-year return for income that PAYE cannot capture — self-employment, rental profits, large investment income or higher-earner charges. Many people use only PAYE; others use both, with PAYE handling the salary and a return reconciling everything else.

The two systems interact. If you owe a relatively small amount through Self Assessment, HMRC can sometimes collect it by adjusting your PAYE tax code in a later year rather than demanding a lump sum. Knowing which system applies to each income source is the first step in checking whether your overall tax is correct, a theme we cover in our guide to the UK Self Assessment return.

How do benefits in kind affect PAYE?

Benefits in kind — company cars, private medical insurance, interest-free loans — are taxable and usually collected through your PAYE code rather than a separate bill. HMRC estimates their value, reduces your tax-free allowance accordingly, and you pay more tax each month as a result. This is often why a tax code is lower than the standard 1257L.

Employers report most benefits on a P11D after the tax year, though many now payroll benefits in real time so the tax is collected as the benefit is provided. Either way, a benefit you forgot about can quietly cut your allowance, so reconciling your P11D against your code each year prevents surprises.

What should employers know about running PAYE?

Operating PAYE is a legal obligation for any business with employees. Employers must register with HMRC before the first payday, deduct the right tax and National Insurance, submit a Full Payment Submission on or before each payday, and pay over the deductions by set monthly or quarterly deadlines. Errors and late submissions attract penalties.

For finance teams, PAYE is also where employer National Insurance — now 15% above a low threshold — and workplace pension contributions are administered. Getting payroll right is therefore both a compliance and a cost-control function, and it links directly to the salary-versus-dividend decisions owner-managers face.

What is a P45, P60 and P11D?

These three forms are the backbone of PAYE paperwork. A P60 is your end-of-year summary showing total pay and tax deducted, issued by your employer after 5 April. A P45 is issued when you leave a job, recording pay and tax to your leaving date so your next employer applies the right code. A P11D reports taxable benefits in kind provided during the year.

Keeping these is essential: you need a P60 to prove income for mortgages or tax claims, a P45 to avoid emergency tax in a new job, and a P11D to reconcile your tax code. Together they let you verify that PAYE has collected the correct tax, which is ultimately your responsibility to check even though the employer operates the system.

How does PAYE handle multiple jobs or pensions?

When you have more than one source of PAYE income, HMRC allocates your Personal Allowance to one of them — usually your main job — and taxes the others at basic or higher rate via codes like BR or D0. If the allocation is wrong, you can overpay on one source while underusing your allowance on another.

This is a frequent source of error for people with a second job, a part-time role alongside a pension, or several small pensions in retirement. You can ask HMRC to split your allowance across sources to match your actual earnings, which smooths the deductions and avoids waiting for an end-of-year refund. Reviewing your codes whenever your income mix changes prevents months of incorrect deductions.

How do I update my details to keep PAYE accurate?

PAYE is only as accurate as the information HMRC holds. Changes in your circumstances — a new job, a company benefit starting or ending, a second income, marriage, or moving in or out of Scotland — all affect your code. You can update most details through your Personal Tax Account on GOV.UK, and HMRC will usually issue a revised code to your employer automatically.

The habit worth building is to check your tax code at the start of each tax year and whenever something changes, rather than waiting for an end-of-year reconciliation. A wrong code corrected in April spreads the fix smoothly across twelve months; the same error found in March forces a sharp adjustment or a refund claim, so early checking is always easier.

Why does PAYE matter for financial planning?

Although PAYE feels automatic, understanding it gives you control over your cash flow and tax efficiency. Knowing how your code works lets you spot errors, time bonuses and pension contributions sensibly, and avoid the emergency-tax trap when changing jobs. For higher earners, coordinating PAYE with pension contributions is the mechanism that manages the £100,000 allowance taper.

For employers and finance teams, PAYE is the front line of payroll compliance and a significant cost centre once employer National Insurance and pensions are added. Treating it as a system to be managed — rather than a black box — improves both individual take-home pay and organisational cost control, which is why it rewards a closer look than most people give it.

A practical example: starting a new job mid-year

Imagine leaving a job in July and starting a new one in September after two months unpaid. Under cumulative PAYE, your new employer — given your P45 — applies the unused Personal Allowance built up during the gap, so your first payslip may show unusually low tax or even a refund as the system rebalances the year. Without a P45, an emergency code could overtax you until HMRC corrects it.

This example shows why the P45 matters and why PAYE is cumulative rather than flat: the system is designed to reach the correct annual total by year-end, smoothing out gaps and changes along the way. Understanding this prevents panic at an odd-looking payslip and helps you spot when a code genuinely is wrong rather than simply catching up.

Common PAYE mistakes and how to avoid them

The most frequent PAYE errors are predictable: starting a job without handing over a P45 and landing on an emergency code; ignoring a tax code that doesn’t match your circumstances; failing to tell HMRC when a company benefit starts or stops; and assuming a second job is taxed correctly when its BR code may not reflect your true overall position. Each can mean months of over- or under-payment.

Avoiding them comes down to a few habits — check every new payslip against your expected allowance, review your code at the start of each tax year, and update HMRC promptly when anything changes. None of this requires expertise, only attention, and it is far easier than reclaiming overpaid tax or settling an unexpected underpayment after the year has closed.

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