Can You Claim Corporation Tax Back? Losses, R&D, and Deadlines

Yes, you can claim corporation tax back whenever your company has paid HMRC more than it actually owed for an accounting period. The refund runs through your Company Tax Return (CT600), and HMRC will transfer the money to your business account, add interest on top, or apply the balance as a credit against future liabilities. The most common routes are carrying a trading loss back against an earlier year’s profits, recovering excess quarterly instalment payments, claiming R&D tax relief, and correcting errors on a return you’ve already filed.

When Your Company Is Owed a Refund

Overpayments happen more often than most directors realise. A handful of situations account for almost all corporation tax refunds:

  • A trading loss in the current period that can be set against profits from the previous 12 months, so HMRC recalculates the earlier year and refunds the difference.
  • Quarterly instalment payments based on forecast profits that turned out to be higher than the year-end figure.
  • R&D tax relief, which for loss-making companies can produce a payable credit paid out in cash even where there is no tax liability to reduce.
  • A large capital purchase mid-year, where the annual investment allowance wipes out taxable profit the company had already been paying instalments on.
  • Errors on a previous return, or a change in how HMRC interprets a treatment, meaning you paid more than the law required.

HMRC pays interest on overpaid corporation tax. As of late 2025 the rate on non-instalment overpayments runs at 3.50 percent.1GOV.UK. HMRC Interest Rates for Late and Early Payments Modest, but on a large overpayment sitting with HMRC for several months it adds up. If your company’s sort code and account number are on the CT600, HMRC transfers what you’re owed automatically.2GOV.UK. Get a Refund or Interest on Your Corporation Tax

Carrying a Loss Back

This is the biggest single route for most companies. Under Section 37 of the Corporation Tax Act 2010, a trading loss can be deducted from total profits in the same accounting period and, if the claim asks for it, from profits in accounting periods falling within the 12 months immediately before the loss period began.3Legislation.gov.uk. Corporation Tax Act 2010 Part 4 Chapter 2 – Trade Loss Relief Against Total Profits HMRC recalculates the earlier year with the loss factored in and refunds the tax you already paid on those now-offset profits.

Two situations extend the 12-month window to three years: terminal losses when a company ceases trading, and losses from ring-fence trades such as oil and gas extraction. Unused losses that you don’t or can’t carry back aren’t wasted, they carry forward against future profits. But carrying forward doesn’t put cash back in the company today.

R&D Tax Relief as a Refund Route

R&D relief is the route where “claiming corporation tax back” most literally means HMRC sending you money you never had. For accounting periods beginning on or after 1 April 2024, most companies claim under a single merged scheme that replaced the previous SME and RDEC regimes, with a credit rate of 20 percent of qualifying R&D expenditure. Loss-making companies where qualifying R&D is at least 30 percent of total expenditure qualify as R&D intensive and can claim under the Enhanced R&D Intensive Support scheme, giving a payable tax credit of 14.5 percent of the surrenderable loss.4GOV.UK. Enhanced Support for Research and Development Intensive SMEs Accounting periods straddling 1 April 2024 may still fall partly under the older SME scheme, where the payable credit was 10 percent or 14.5 percent of the surrenderable loss depending on whether the intensity condition was met.5GOV.UK. Research and Development Tax Relief for Small and Medium-Sized Enterprises The qualifying expenditure and credit go in the designated R&D boxes on the CT600.

How to Claim the Money Back

The route depends on whether the return for the relevant period has already been filed.

If you’re filing the return now. Enter the loss carry-back figures in the losses and capital allowances section of the CT600, and any R&D credits in the tax reliefs boxes.6GOV.UK. Corporation Tax Company Tax Return CT600 Submit online through commercial accounting software or an agent.7GOV.UK. File Your Accounts and Company Tax Return Confirm that a repayment is due and include your bank details on the return. Save the submission receipt with its reference number in case you need to follow up.

If the return has already been filed. Amend it. Amendments must normally be made within 12 months of the filing deadline for that return.8GOV.UK. Company Tax Returns – Making Changes You can amend through commercial software or by sending a paper return to HMRC’s Corporation Tax office.9GOV.UK. Filing Company Accounts and Tax Returns if You Previously Used the HMRC Online Service The software recalculates the amended liability and flags the resulting overpayment to HMRC.

If the 12-month amendment window has closed. Overpayment relief is the backstop, available up to four years from the end of the accounting period.10GOV.UK. SACM12155 – Overpayment Relief – Time Limits for Making a Claim You’ll need to show the original tax was paid under a mistake, whether a factual error in the return or a misunderstanding of the rules. The claim is made separately from the ordinary amendment process and has its own procedural requirements.

What You Need Before You File

Have these ready:

  • Your company’s Unique Taxpayer Reference, a 10-digit number from previous tax returns or HMRC correspondence.11GOV.UK. Find Your UTR Number
  • The exact accounting period dates for the loss or overpayment. Getting these wrong triggers rejection.
  • The CT600 itself, with reliefs and repayment request entered in the right boxes.
  • Your company sort code and account number. HMRC processes refunds significantly faster with bank details on file; without them you may get a cheque instead.
  • Supporting calculations: a clear loss computation showing which prior period’s profits are offset, detailed qualifying expenditure for any R&D claim, and capital allowance schedules. Well-documented claims are less likely to attract an enquiry.

Wrong bank details are a surprisingly common cause of delays. Check the digits against a recent statement before submitting.

Deadlines

Three separate time limits apply, and missing them means losing the refund permanently:

The four-year overpayment relief window is the one most companies don’t know about. If the error is on a return from three years ago and the amendment deadline is long gone, overpayment relief is the only route left.

How Long the Refund Takes and How It’s Paid

HMRC doesn’t publish a guaranteed processing time. Straightforward claims that match HMRC’s records tend to go through within a few weeks. More complex claims, high-value refunds, and first-time claimants without an established filing history attract more checks and take longer. Every round of correspondence with HMRC can add weeks. You can check whether a return has been received and see expected reply times through HMRC’s online services.12GOV.UK. Check When You Can Expect a Reply From HMRC

Refunds go by direct bank transfer where details are on the CT600. Otherwise HMRC may send a cheque to your registered office, or apply the overpayment as a credit against future corporation tax liabilities.2GOV.UK. Get a Refund or Interest on Your Corporation Tax Companies on quarterly instalments sometimes assume HMRC will automatically pay out any overpayment. It generally won’t. Absent specific bank details and a repayment request on the return, HMRC applies the balance as a credit.

What Can Go Wrong

The biggest practical risk is filing a claim that triggers an HMRC enquiry. HMRC can open an enquiry into any Company Tax Return within 12 months of the filing date, and certain claims attract closer scrutiny. R&D relief is a well-known trigger, especially for first-time claimants and sectors where HMRC has seen patterns of overclaiming. An enquiry doesn’t mean the claim is wrong, but it freezes the refund until HMRC is satisfied.

Other common problems: claiming losses against the wrong accounting period, entering incorrect bank details, and missing the two-year loss carry-back deadline. And if HMRC concludes a claim significantly understated the company’s tax liability through negligence or disregard of the rules, penalties and interest apply on any amount you received but weren’t entitled to. The best protection is keeping loss computations, R&D project records, and capital allowance schedules in order before you submit, not after HMRC asks for them.