Can I backdate my R&D tax relief claim?
Yes, R&D tax relief claims can be backdated for two years from the end of the accounting period in which you did the R&D project.
This two year deadline is to marry up with the Corporation Tax 24 month rule. You have 24 months to make any necessary changes to your Corporation Tax Return after the end of its accounting period.
Start Ups follow the same R&D tax relief deadline
Your first accounting period is measured as twelve months from the end of the month you register with Companies House. Lots of companies want to align their accounting period more conveniently and so change their dates. This means that your first two accounting periods may be less than the full twelve months.