05/05/2026
You probably left R&D tax relief unclaimed last year.
Here is the check:
Step 1 — Does your work qualify?
Find one project where you did not know at the start whether it would work technically. That uncertainty is what HMRC is looking for. One project is enough.
Step 2 — What costs count?
Staff time: salary × the percentage spent on that work.
Subcontractors: 65% of what you paid them.
Software licences used in the process.
Step 3 — What is it worth?
Add up your qualifying costs. Multiply by 186%.
Apply your corporation tax rate.
At 19%, that is 35p back for every £1 of qualifying spend.
Three things to do before you file:
→ Check the last two accounting periods — both are claimable.
→ Submit the Additional Information Form before the CT600.
→ Raise it with your accountant now, not after the deadline.