If you’ve paid more Self Assessment tax than you owe, you can get the money back by claiming a Self Assessment overpaid tax refund either on your tax return or through your HMRC online account once a credit shows on your record. HMRC usually pays by BACS transfer to the bank details you provide, and you have four years from the end of the relevant tax year to claim.
Confirm the Overpayment First
Before requesting anything, check the numbers. Your SA302 tax calculation shows your total income, allowances and reliefs, the tax due, and how HMRC arrived at the figure. You can view it online for the last four years once your return has been filed.1GOV.UK. Understand Your Self Assessment Tax Bill – Tax Calculation SA3022GOV.UK. Get Your SA302 Tax Calculation
On your HMRC online account, a credit balance appears as a negative figure in the “Amount to pay” section. That minus sign means HMRC owes you. Cross-check it against the SA302 breakdown and look at each component separately: income tax, Class 4 National Insurance, and any student loan repayments. A mismatch suggests either a data entry error or an adjustment HMRC has made, and it’s worth querying that before you request the refund.
How to Claim the Refund
On Your Tax Return
The simplest route is to claim when you file. The SA100 return has a section on page 6 (boxes 4 to 14) where you enter your bank details: account holder name, sort code, and account number. If HMRC’s calculation confirms a credit after processing, the refund goes to those details automatically. No separate claim needed.
After You’ve Already Filed
If the return is already in and a credit later appears on your account, request the refund through your HMRC online account. Go to the Self Assessment section and look for the repayment option, which shows up once the system recognises a credit balance.3GOV.UK. Self Assessment Tax Returns – Claiming a Tax Refund You’ll need your Government Gateway credentials (the 12-digit User ID and the password you set up when registering) along with a UK sort code and account number.
One quirk catches people out. If your most recent payment to HMRC was by debit or credit card, the system may refund to that card automatically rather than to the bank account you specify. HMRC applies this when the card payment was made within the previous nine months and the refund does not exceed that payment. There is no way to override it. If the card has since expired or been cancelled, contact HMRC to arrange an alternative.
A Note on Form R40
Form R40, used to reclaim tax on savings and investment income, is not available to anyone registered for Self Assessment. If you’re in Self Assessment, the return itself is the route.4GOV.UK. Claim a Refund if You’ve Paid Tax on Your Savings and Investments
How HMRC Sends the Money
The default is a BACS transfer straight into the account you gave. It’s the fastest option and the one HMRC uses whenever valid bank details are on file.
If HMRC holds no bank details, it posts a payable order to the address on your tax record. A payable order works like a cheque. HMRC’s process is that a payable order is posted 21 days after notification that a refund is due, when no electronic payment method is available.5GOV.UK. Taxpayer Experience of the HMRC Repayments Process Deposit it promptly; payable orders can expire, and a stale one has to be replaced by contacting HMRC.
You can also leave the credit sitting on your account. If your next payment on account is due soon, the balance offsets against the 31 January or 31 July payment automatically, saving you a transfer.6GOV.UK. Pay Your Self Assessment Tax Bill
How Long It Takes
Timelines depend on how you filed and whether HMRC runs security checks. Online returns move faster than paper ones. A straightforward online claim can be paid within a few working days; a paper return with queries attached can stretch out to around eight weeks. The BACS transfer stage itself, once approved, runs to about five working days.7GOV.UK. PAYE Manual – PAYE91037 – Reconcile Individual: Overpayments: Repayments by BACS Process
You can track progress with the “Check when you can expect a reply from HMRC” tool, which is updated weekly and estimates a response date based on current workloads.8GOV.UK. Check When You Can Expect a Reply From HMRC
When HMRC Holds Back Some or All of It
Before releasing anything, HMRC checks whether you owe elsewhere. If a Self Assessment payment is due within the next few weeks, HMRC will typically reduce the refund by the amount needed to cover it. Overpay by £2,000 with a £1,500 payment on account due shortly, and HMRC may release only £500, holding the rest against the upcoming bill.
HMRC can also offset your overpayment against other tax debts, such as a tax credits overpayment. Don’t assume the full credit balance will land in your bank account if you have outstanding amounts anywhere in the HMRC system.
The Four-Year Deadline
You cannot leave an overpayment claim sitting indefinitely. The general rule is four years from the end of the tax year the overpayment relates to. For the 2025–26 tax year, which ends on 5 April 2026, the deadline to claim is 5 April 2030.9GOV.UK. Self Assessment Tax Returns – Deadlines After that date the money is gone. If you suspect an overpayment from a few years back, check now.
Interest HMRC Pays on Late Refunds
HMRC pays interest when it holds your money longer than it should, though the rate is modest. The repayment interest rate is 2.75% from 9 January 2026.10GOV.UK. Rates and Allowances – HMRC Interest Rates for Late and Early Payments That sits well below the rate HMRC charges for late payments. Repayment interest runs from the date the overpayment arose, so there is some compensation for delays, but it won’t make you whole if a large refund sits in limbo for months. Filing early with bank details entered upfront is the most reliable way to avoid the wait.
Stopping the Overpayment Before It Happens
If you already know this year’s income will be lower, you don’t have to wait until filing to get money back. You can apply to reduce your payments on account through the HMRC online service or by posting a paper form. You qualify if business profits or other income have dropped, tax relief entitlements have gone up, or more of your tax is now deducted at source than in the prior year.11GOV.UK. Claim to Reduce Payments on Account The deadline to apply is 31 January after the end of the tax year.
One caution. If you cut your payments on account by too much and your actual liability turns out higher, HMRC will charge interest on the shortfall for the period the tax was outstanding. Penalties can apply in theory if the reduction was fraudulent or negligent, but in practice HMRC rarely pursues them unless the false claim was blatant or part of a pattern.12GOV.UK. Enquiry Manual – EM4660 – Penalties: Claims to Reduce Payments on Account A reasonable estimate made in good faith is unlikely to cause trouble even if it turns out slightly wrong.