Fix a Wrong Tax Code and Claim Overpaid Tax Refund

Complete guide to correcting wrong PAYE tax codes and emergency tax. Learn how to check your coding via Personal Tax Account, P800 reconciliation, overpayment refund claims, and 4-year refund limits.

Quick Answer

Wrong PAYE tax codes cause overpayment of tax - you may be owed a refund. Check your code immediately via HMRC Personal Tax Account (easy online access). If your code is wrong (shows fewer allowances than entitled), report it to HMRC immediately for correction. HMRC will adjust future pay or issue a refund. For past overpayments, use form P800 (sent annually by HMRC) or claim direct if you have a payslip showing wrong code. You can claim back 4 years of overpaid tax. Average overpayment claims: £500-£2,000. This is free; HMRC handles refunds directly. Emergency tax code (code 0T) must be corrected within 60 days or you may be owed interest.

How to Fix Wrong Tax Codes and Claim Refunds

1

Check Your Current Tax Code

Log into HMRC Personal Tax Account (gov.uk). Navigate to "Income and earnings" - "PAYE" section. Your current tax code is displayed (e.g., 1257L, 0T). Compare to your payslip. Your code determines how much tax is deducted: lower code = more tax deducted. Check if you have claimed all applicable allowances (marriage allowance, personal savings, trading allowance). If code is lower than expected, it's likely wrong.

2

Report Wrong Code to HMRC (Immediate)

Call HMRC Self Assessment phone line (0300 200 3300) or message via Personal Tax Account. State the wrong code, why it's wrong (missing allowances, wrong employer details), and provide payslips as evidence. HMRC corrects code for current and future pay. Request written confirmation of the correction. If code was wrong due to HMRC error (not your fault), HMRC may backdate correction and issue refund automatically.

3

Claim Overpaid Tax (P800 or Direct)

HMRC sends P800 (Statement of Earnings) annually showing overpayment due. Accept refund offer on P800 or claim direct if you don't receive P800. Alternatively, use payslips showing wrong code applied to claim refund in writing. HMRC issues refund within 4-8 weeks. You can claim back 4 years: current year plus prior 3 years. For emergency tax (0T code), claim within 60 days for guaranteed correction; after 60 days, you may face interest delays.

What the Law Says

Income Tax (PAYE) Regulations 2003
Employers must operate PAYE using the tax code provided by HMRC. HMRC must issue correct codes based on the information available. If an employee has additional allowances (e.g., marriage allowance, trading allowance), HMRC must include them in the code. Wrong codes are HMRC errors; employees are entitled to refunds of overpaid tax.
Limitation Act 1980, s.5 (4-Year Refund Limit)
You can claim overpaid tax back 4 years. For example, if it's 2026, you can claim overpayments from 2022 onwards. Claims older than 4 years are time-barred (cannot be recovered) unless you have special circumstances (HMRC error, previous awareness). HMRC voluntarily refunds within 4 years even without formal claim.
Income Tax Act 2007, s.835 (Allowances)
Every individual is entitled to personal allowance (currently £12,570 for 2024-25). Additional allowances include: marriage allowance, savings allowance, trading allowance (self-employed). HMRC codes must reflect entitlements. If a code excludes entitled allowances, it is wrong and must be corrected.
PAYE Emergency Code Rules
Code 0T (emergency code) is temporary, issued when no information is available (new job, returns submitted late). Employers must not apply code 0T beyond 60 days without notice. If code 0T is applied incorrectly or beyond 60 days, you are entitled to refund of overpaid tax. HMRC must correct automatically.

Common Wrong Tax Code Scenarios

Missing Marriage Allowance

You're eligible for marriage allowance (spouse's unused allowance transferred). Code shows lower allowance. Report to HMRC; claim backdated to start of marriage. Refund can be £100-£300 per year for each year eligible.

Emergency Code (0T) Not Corrected

You started a job; employer applied code 0T. HMRC should have corrected it within 60 days. If still 0T after 60 days, you've overpaid. Contact HMRC immediately; claim refund. Emergency codes often result in £500-£1,500 overpayment.

Trading Allowance Missing (Self-Employed)

You're entitled to trading allowance (£1,000 self-employed income tax-free). PAYE code doesn't reflect it. Report to HMRC; code corrected. Refund due if overpayment occurred from prior year.

Blind Person's Allowance Not Applied

You registered as blind or visually impaired. Tax code doesn't show blind person's allowance (additional £2,870 per year 2024-25). Report to HMRC with registration proof; claim refund. Can be significant if overlooked for multiple years.

Savings Allowance Missing

You're a basic rate taxpayer eligible for £1,000 savings allowance (interest earned tax-free). Code doesn't reflect it. Inform HMRC; code corrected. Refund issued if overpaid on savings interest.

Second Job Tax Code Wrong

Your second job PAYE uses code BR (basic rate, full tax) instead of 0T (no allowance). You're overpaying because allowance used by first job. HMRC can correct to 0T; claim refund of overpaid tax on second job income.

Frequently Asked Questions

How do I check my tax code online? +
Log into HMRC Personal Tax Account at gov.uk using your UKI or Government Gateway login. Go to "Income and earnings" - "PAYE". Your current code appears (e.g., 1257L, 0T). Also check your latest payslip; code is shown in the top right corner.
How long does HMRC take to refund overpaid tax? +
4-8 weeks for most refunds. If code is corrected mid-year, HMRC adjusts future pay (faster than refund). For P800 refunds, HMRC processes within 4 weeks. Direct claims can take 8-10 weeks. Interest is not charged on delayed refunds.
How far back can I claim overpaid tax? +
4 years. For example, in 2026 you can claim from 2022 onwards. Claims older than 4 years are time-barred except in cases of HMRC error or established practice where HMRC voluntarily refunds.
What is emergency code 0T? +
Code issued when no information is available (new job, return not submitted). Means full tax is deducted; no allowance. Must be corrected within 60 days. If not corrected, you've overpaid significantly and can claim refund.
Can I claim refund if I received a wrong code but didn't report it? +
Yes. Even if you didn't report it, if the code was wrong (not your mistake), HMRC must refund overpaid tax. HMRC errors are their responsibility. You can claim within 4 years whether you reported it or not.
What if my employer calculated tax using a wrong code intentionally? +
This would be illegal. Employers must use the HMRC code provided. If intentional underpayment, report to HMRC and your employer is liable. For overpayment by error, claim refund from HMRC. If your employer refuses to cooperate, contact HMRC Employer Compliance.

Claim Your Tax Refund Now

Use FightingBack's Tax Tool to calculate your overpayment and prepare a refund claim.

Check Your Overpayment