Check your tax code before it costs you
A wrong PAYE code is one of the most common reasons people overpay or underpay Income Tax during the year.
Your tax code tells your employer how much Income Tax to deduct. The standard code for someone with a full £12,570 Personal Allowance is often 1257L, but benefits, second jobs, underpayments and Marriage Allowance can change the numbers and letters. Checking it takes minutes and can reclaim hundreds of pounds.
Where to find your code
Look at your payslip, your personal tax account on GOV.UK, or HMRC notices. Each employer and pension payer may use a code. Two jobs often mean one main code with allowance and a second code like BR (basic rate on all income from that job) — that can be correct, but it needs a sanity check.
Common codes and what they hint at
1257L — usually full Personal Allowance. Emergency codes (often with W1/M1) — temporary; tax may be collected on a non-cumulative basis and need sorting. BR, D0, D1 — tax all income from that source at basic, higher or additional rates. K codes — deductions exceed allowances (for example large benefits).
Letters still matter: L is common; M or N can relate to Marriage Allowance; S or C can indicate Scottish or Welsh rates.
How codes go wrong
Starting a job without a P45, overlapping employments, company cars, changing benefits mid-year, or HMRC estimating side income can all skew the code. Sometimes you overpay for months then receive a refund after a reconciliation; sometimes you get a surprise bill.
If your code embeds an underpayment, HMRC is collecting old tax via PAYE. That may be intentional — still confirm the amount is right.
How to fix it
Update your personal tax account, send an income update, or contact HMRC with evidence (P45, benefit letters). Employers cannot invent a kinder code; they must follow HMRC. Keep payslips until the tax year is reconciled.
After a fix, watch the next two payslips. Year-to-date tax should start making sense against the £12,570 allowance and your band.
Worked example: emergency code cost
Sam starts a £32,000 job in May without a P45 and is put on an emergency code. For three months Sam pays noticeably more tax than a colleague on 1257L. After HMRC issues the correct cumulative code, later payslips reduce deductions and Sam’s personal tax account shows a refund due of several hundred pounds. Checking the code in week one would have avoided the cash-flow hit.
Step-by-step checklist
- Read the tax code on your latest payslip
- Compare it with your HMRC personal tax account
- List all jobs, pensions and taxable benefits
- Note whether a second job uses BR or similar
- Act quickly on emergency codes after a job change
- Keep P45/P60 records for at least the current and prior year
- Re-check after Marriage Allowance or benefit changes
Common mistakes
- Assuming the employer “sorted tax” without looking at the code
- Ignoring a W1/M1 emergency basis for months
- Forgetting a second small job still needs a correct code
- Throwing away P60s before checking a possible refund
When to get regulated help
Use your personal tax account on GOV.UK to view and update codes. For independent explanations of payslip terms, visit MoneyHelper.
Frequently asked questions
What does 1257L mean?
It usually means you receive the standard £12,570 Personal Allowance, with L indicating the basic personal allowance situation.
Can I ask payroll to change my code?
Payroll must use the code HMRC supplies. You fix issues with HMRC, then payroll follows the update.
Why is my refund not instant?
HMRC may adjust via PAYE over remaining months or pay a refund after processing — timing varies.
Do pensioners have tax codes too?
Yes — pension payers use tax codes, and multiple pensions can create the same second-income issues as second jobs.