5.6 Million People Overpaid Tax. Are You One of Them?
A new analysis of HMRC's own PAYE data has uncovered something most taxpayers never see coming — and HMRC isn't required to tell you if you're affected.
The analysis comes from accountancy group UHY Hacker Young, who examined HMRC's own PAYE figures through a Freedom of Information request. The tax code — the string of numbers and letters that tells your employer or pension provider exactly how much to deduct from your pay — is meant to reflect your exact circumstances. When it's wrong, the numbers speak for themselves.
The Evidence: Why Tax Codes Go Wrong
Tax code errors aren't random — they follow a pattern. Here's what usually causes them, according to HMRC's own guidance.
Job Changes
Switched employer in the last 12 months? Your new employer may still be operating on outdated information from your previous role.
Multiple Income Sources
Two jobs, a job plus a pension, or freelance income on the side can confuse how your tax-free allowance is split.
Benefits-in-Kind
A company car, private healthcare, or gym membership you no longer receive can still be sitting on your record, quietly reducing your allowance.
Incomplete Employer Information
HMRC relies on your employer submitting accurate, timely data — when that data is late or wrong, your code inherits the error.
Are You More Likely to Be Affected?
Certain situations make a tax code error far more likely. If any of these apply to you, it's worth checking.
The Part Most People Miss
Refunds aren't automatic in every case — the responsibility to check, and to claim, sits with you.
How to Check Your Own Tax Code
This takes about five minutes, and it's the only way to know for certain whether you're one of the 5.6 million.
Find your current tax code
Check your latest payslip, P60, or P45 — it's printed clearly on each.
Compare it against reality
Log into your HMRC Personal Tax Account and check what income, jobs, and benefits are on record.
Flag any mismatch
An old company car, a job you left, or a missing pension can throw your code off — correct it as soon as you spot it.
Claim back what's owed
If your code has been wrong, you can usually claim overpaid tax for up to four previous tax years.
Common Questions
Will HMRC automatically refund me if I overpaid?
Not always. HMRC may send a P800 or Simple Assessment letter after the tax year ends, but it isn't guaranteed — especially if HMRC's records are out of date.
How far back can I claim an overpayment?
Generally, up to four previous tax years — so it's worth checking more than just your current code.
What if I have a second job or a pension?
This is one of the most common triggers for a wrong tax code — HMRC has to correctly split your allowance across each source.
Where do I check officially?
Through your HMRC Personal Tax Account, your payslip, or your P60/P45.
Don't Want to Chase This Yourself?
Reviewing a tax code and dealing with HMRC to get it corrected and refunded takes time most people don't have. We do this for clients regularly — quietly, accurately, without the hours on hold.
Tax Code Review
We check your current code against your real circumstances and flag exactly what's wrong.
HMRC Correction & Refund Claims
We deal with HMRC directly to get your code fixed and any overpaid tax claimed back.
Multi-Income Situations
Two jobs, a pension, or freelance income on the side — we make sure it's all reflected correctly.
Think You're Owed Money?
Let us check your tax code and find out — no cost to look, and no jargon to wade through.
Book a Free Consultation Email UsData source: Analysis of HMRC PAYE data by UHY Hacker Young (Freedom of Information request, 2023/24 tax year figures). Official HMRC guidance on tax codes — gov.uk/tax-codes and gov.uk/check-income-tax-current-year.
This article is for general information only and is not a substitute for professional tax advice specific to your business.