What Happens If You Overpay Income Tax in the UK?

If you've overpaid income tax, you've basically given HMRC an interest-free loan. They won't thank you for it, but they will give it back. Eventually.

Tax overpayments are more common than you'd think. HMRC issued over 8 million P800 calculations in recent years, and a good chunk of those were refunds. Here's why it happens, how to check, and what to do about it.

Why overpayments happen

The PAYE system tries to spread your tax bill evenly across the year. When something changes mid-year, the maths goes wrong. The most common reasons:

Wrong tax code. Your tax code tells your employer how much tax to deduct. If it's wrong, every payslip is wrong. This happens more often than you'd expect, especially after life changes like getting married, starting a pension, or paying off a company car.

Changing jobs. When you switch employers, there's often a gap or overlap where PAYE doesn't quite sync up. Your new employer might not have your P45 yet, or they might apply your personal allowance incorrectly.

Emergency tax. Start a new job without giving your employer a P45 and you'll likely be put on an emergency tax code. That usually means paying too much until it's sorted.

Multiple jobs. If you have two employers, HMRC splits your personal allowance between them. If the split is wrong (and it often is), one job overtaxes you.

One-off payments. A bonus, redundancy payment, or large commission can temporarily push you into a higher tax band. PAYE sometimes overtaxes these because it assumes every month will be the same.

How HMRC spots overpayments

After the tax year ends on 5 April, HMRC runs a reconciliation. They compare what you actually earned with what you actually paid.

If they find you've overpaid, they'll send you a P800 tax calculation, usually between June and October. This letter (or online notification) tells you exactly how much you're owed.

You can then claim the refund online through your personal tax account and get paid within five working days. If you don't claim within 45 days, HMRC posts a cheque.

If you file a Self Assessment return, any overpayment shows up when you submit. HMRC either refunds it or offsets it against your next tax bill, your choice.

How to claim a refund yourself

Don't want to wait for HMRC to get around to it? You can be proactive:

Step 1: Check your tax code. Log into your personal tax account and see if your code matches your situation. The code 1257L is the standard one for 2025/26 (it means you get the £12,570 personal allowance).

Step 2: Gather your paperwork. P45 from your old employer, P60 from year-end, recent payslips, and any HMRC letters.

Step 3: Claim online. For most PAYE overpayments, use the claim a tax refund service on GOV.UK. It's the fastest route.

Step 4: Call if needed. For complicated cases (multiple employers, overseas income, benefits in kind), the income tax helpline can sort it out. Expect a wait, especially in January and April.

How long refunds take

Claim method	Typical timeframe
Online (via personal tax account)	5 working days
P800 cheque (if you don't claim online)	45 days after P800, then a few weeks
Postal claim	Up to 8 weeks
Self Assessment (after filing)	5-10 working days

If you've recently moved, update your address with HMRC first. Cheques sent to old addresses are the most common reason refunds get lost.

Real examples

Priya changed jobs in September. Her new employer didn't receive her P45 for three weeks, so she was put on an emergency tax code. She overpaid by £380 over two months. HMRC caught it in their end-of-year check and sent a P800 in July. She claimed online and had the money back within a week.

Marcus had two part-time jobs. HMRC allocated his full personal allowance to one job and gave the other a BR (basic rate) code, meaning every penny from the second job was taxed at 20% with no allowance. He was overpaying by about £60 a month. He called HMRC, got his codes corrected, and received a £540 refund for the year.

Fiona received a £5,000 bonus in March. PAYE treated it as though she'd earn that much every month, pushing her into the higher-rate band for that pay period. The overpayment of £220 was automatically corrected over the following months through cumulative PAYE adjustments.

Mistakes to avoid

Don't ignore your tax code. It's a few letters and numbers on your payslip. If it changes unexpectedly, find out why.

Don't assume HMRC will always catch it. They usually do for PAYE workers, but not always quickly. If something looks off, check yourself rather than waiting a year.

Don't fall for "tax refund" scam texts and emails. HMRC will never email or text you asking for bank details or linking to a refund form. If you get one, it's a scam. Always go directly to GOV.UK.

Time limits

You can claim a tax refund for the current year plus the previous four tax years. In 2025/26, that means you can still reclaim overpaid tax going back to 2021/22.

Once the four-year window closes, the money is gone. So if you suspect you've been overpaying for a while, don't sit on it.

To see how much tax you should be paying on your current salary, try our salary calculator.