When do I need a Claim Notification Form for R&D?

If you’re claiming for the first time and your period of account began on or after 1 April 2023, you may need to submit a claim notification form (CNF). The deadline to file is six months after the end of this period of account. So, if your period of account ended 31 May 2025, the deadline to file your CNF will be 30 November 2025.

CNFs let HMRC know you’re intending to file a tax credits claim. Filing correctly and on time prevents delays in receiving your R&D benefit. You don’t need to submit a CNF if you made a valid R&D claim in the last three years, unless this claim was rejected, or you amended your tax return on or after 1 April 2023.