To begin with, a claim has to be made. That is something which many companies and quite a few accountants have yet to grasp.
The claim can be submitted as soon as is practical, even before April 5 but only as long as the final EPS and FPS have been submitted, which need to declare the deductions that have been made from the income of the company. Bear in mind, though, that HMRC need a couple of weeks to collate all of the information received from all contractors into an accessible format. Processing of repayment claims can begin from April 22.