They should only be used for residential leases. Mailed payments can only be in the form of a money order, cashier's check or business check.Complete the relevant application form. Submit the form to The Clerk. Failure to do so will diminish your score. A sample of an affidavit of service is attached. Please refer to the annotated image and instructions below to learn how to fill out a check for your OPT application. Attached RFP Response Form.