Gift Aid claims

We are a recently, Feb 24, registered cat charity and we wish to claim gift aid. We have registered with HMRC and sent out gift aid declarations. I believe that we are able to claim gift aid for the last 4 years.

Is there a set date that we can send our gift aid claim into HMRC? I have a business and send my tax returns in by 31/1 for the previous year, is this the dame for claiming the gift aid or are we able to file any time?

Thank you