My project needs a certification for this appraisal. By when should I get it done

Which Certification ?

Ideally, before the 31st of March this year. Remember, appraisal works in the current FY, so everything needs to be done before this FY ends.

But it also depends on your manager and project too. Right now they looking for reasons not to give a person a good band so if bands your goal try finishing it up asap.