R&D claim notification form deadlines: When and how to submit

A critical deadline may be approaching for your business if you’re planning to make an R&D claim for your current accounting period. Under HMRC’s rules, companies that are required to submit a claim notification form must do so within six months of the end of the relevant accounting period.

What is a claim notification form?

The claim notification form is a mandatory form introduced by HMRC to improve oversight and compliance around R&D tax relief claims. It must be submitted before the company files its corporation tax return if any of the following apply:

• The company is claiming R&D tax relief for the first time
• The company has made a claim more than three years before the last date of the claim notification period, or
• The company has made a claim within the within the last three years but does not meet the transition criteria below

Who needs to submit an R&D claim notification form?

This requirement can easily be overlooked, especially by companies that:

• Are newly incorporated and unfamiliar with the rules
• Have previously submitted claims via amended tax returns
• Use separate agents for R&D claims and general tax compliance

Even if your company has made an R&D claim in the past, you may still need to submit the notification form depending on when and how the previous claim was filed.

Transitional rules and exceptions for the R&D claim notification form

First, newly incorporated companies might assume they have the standard two-year amendment window to make an R&D claim. They therefore overlook the notification window which closes six months after the year end.

Secondly, even if you’ve made an R&D claim in the past three years, you may still need to submit a claim notification form. However, transitional rules state that claims for periods beginning before 1 April 2023. If submitted after that date via an amended tax return should be ignored for this purpose.

This can (and will) catch many companies and advisors out. It’s especially common when a separate agent handles the R&D claim while the company’s main tax advisors remain unaware of the notification requirement. This is a common scenario — many companies submit their R&D claims through amended tax returns rather than the original filing, which can lead to confusion about deadlines and eligibility.

For example, a company may have previously submitted an R&D claim for the year ended 31 March 2023 via an amended return in March 2024. As this was a claim related to a period beginning before 1 April 2023, and submitted as part of an amended tax return after 1 April 2023, it is to be ignored for these purposes.

If you are unsure whether this requirement applies to you, we recommend checking with your tax advisors.

Missed the claim notification window?

Missing the claim notification window for a given accounting period will prevent a company from making an R&D claim for that period. Therefore, it is important to check that your company does not miss the claim notification window. This is particularly relevant for companies with a 31 March year end.

If a claim notification form is required for your current accounting period, the deadline depends on your year end:

• 30 September for companies with a 31 March year end
• 30 June 2026 for companies with a 31 December year end.

Further details of the claim notification requirements can be found here.