How far back can you claim R&D tax credits? You’ll be glad to hear the system is quite generous: you can claim for up to 24 months after the end of your accounting period. 

However, there’s an exception to the rule for companies that haven’t made a claim in the last three years. Don’t worry though: in this blog post, we explain everything you need to know. 


R&D accounting periods

R&D tax credits are a form of corporation tax relief, and 24 months is the time limit you have to revise your corporation tax return. That’s why you have two years to make a retrospective claim.

Accounting periods are typically 12 months long. Therefore, if your accounting period end date is 31 March, you’ll have to submit your R&D tax credit claim for 1 April 2021 to 31 March 2022 two years later by midnight on 31 March 2024.

Be aware, however, that as soon as you reach your R&D claim deadline, you can no longer recover the money you spent on qualifying costs over the accounting period. 

If you want to prolong your R&D claim period, you can change your accounting periods. If you want, you can lengthen it to 18 months.

Alternatively, you can also shorten the accounting period if you’ve started an R&D project that you’d like to receive credit for sooner. 


R&D claims outside the two-year limit

Although HMRC thinks two years is ample time to submit R&D credit claims, it does accept there are exceptional circumstances that might mean a claim isn’t made within the time limit.

For instance, HMRC may still accept claims outside the two-year limit if the cause is “beyond the company’s control”. Two examples include:

  • when the company or its agents are unaware of profits against which the company could claim relief
  • there is a delay in agreeing the amount of profit or loss in discussion with HMRC but the delay is not the company’s or its agents’ fault.

Therefore, if you’re concerned you’ve missed the time limit to make a retrospective claim, don’t assume that you actually have — talk to an agent to find the best way forward.


First-time or irregular R&D claims

Since April 2023, a new rule exists for companies that haven’t made an R&D credit claim in the last three calendar years. 

According to the new rule, these companies must inform HMRC they intend to make a claim within six months after the accounting period the claim relates to. They can do that with a claim notification. 

The Government introduced this 6-month window rule for irregular/new claims to “tackle abuse and improve compliance”. If you fail to make a claim notification, your later claim won’t be valid.


Need help with your R&D claim?

We’re accountants who can help you claim R&D tax relief from start to finish. Feel free to get in touch with us to discuss your claim.