An application for an agreement in principle must be submitted by the applicant before the start of any energy retrofitting work. If the applicant changes the retrofitting concept on the advice of the energy adviser, after the agreement in principle has been reached, the applicant may submit an application for a new agreement in principle. This request is optional. If the applicant wishes to ensure that the modified retrofitting concept remains eligible, it is essential that they submit a new application for an agreement in principle.