An Acknowledgment of Paternity (AOP) is a legal document that allows parents who aren't married to establish legal paternity. Per a new state law, Tarrant Appraisal District is sending homeowners letters asking them to confirm their homestead exemption.The Acknowledgment Letter will serve as proof that the non-resident attorney has satisfied the required fee. An acknowledgment is one of the most common types of notarial acts, but it often confuses Notaries. Here are 5 steps to performing an acknowledgment.