Wrong Tax Code? Checks and Correction Steps

Open HMRC’s Check your Income Tax service or the HMRC app. Select the relevant job or pension. Compare its current code and explanation with your payslip and any coding notice you received. An older payslip can legitimately show an earlier code.

Review the underlying records as well as the code: estimated annual income, employment end dates, pensions, company benefits and expenses. For example, an old job still recorded as active is something to investigate; it does not by itself prove how much tax you overpaid.

• HMRC shows a new code but your payslip uses the old one: ask payroll whether they received the notice and which payday will use it. Employers retrieve notices through PAYE Online, the Desktop Viewer or supported payroll software.
• The payslip and HMRC code match, but a benefit ended or an income estimate is wrong: update the relevant details with HMRC. Payroll applying the issued code correctly does not prove the underlying information is correct.
• The code matches but the tax amount looks unusual: ask payroll to check taxable pay, previous pay and tax, and the cumulative or non-cumulative basis. A bonus, pension method or year-to-date adjustment can explain the difference.

A useful question is: “My HMRC account shows [code] for this employment, but my payslip dated [date] shows [code]. Which notice and pay-to-date figures were used?” Your employer can investigate their payroll records; HMRC handles changes to the information behind an issued code.

Give your new employer your P45, or complete the starter checklist if you do not have one. W1, M1, X or NONCUM means earlier periods are not included in that pay-period tax calculation. It does not establish that a refund is due.

HMRC says to allow 35 days after starting a job for the new income information to arrive before contacting them about a code that still looks wrong. You can check the details and give payroll missing starter information in the meantime. Follow the current HMRC correction guidance for your situation.

Where a change is needed, HMRC says it will notify you and your employer within 15 working days. For monthly pay, the new code should appear on the next or following payslip; for weekly pay, on the third payslip. Check with payroll if it has not appeared.

A refund depends on the complete income and tax records. If HMRC has the information needed and you overpaid, it normally arranges repayment through your employer or pension provider when the new code is used. Missing records can delay this, and a non-cumulative code does not automatically reconcile earlier periods.

After the tax year, HMRC may send a tax calculation explaining an overpayment or underpayment and what to do. Follow that calculation or the official refund guidance; a code change is not a guaranteed refund on the very next payday.

This annual 2026/27 illustration assumes one £35,000 job in England, Wales or Northern Ireland, entitlement to the full £12,570 Personal Allowance, and no pension, benefits or other income affecting Income Tax.

Annual Income Tax illustration, not a payroll refund calculation

Code	Income Tax for the year
BR	£7,000
1257L	£4,486

BR gives £35,000 × 20% = £7,000. With the full allowance, (£35,000 − £12,570) × 20% = £4,486. The difference is £2,514 a year, or £209.50 averaged over 12 months. This is not evidence that every employee with BR should have 1257L: another job or pension may already use their allowance.

Open the £35,000 BR example or the £35,000 standard-code example to explore the assumptions. The calculator cannot determine which code HMRC should issue to you.