For an acknowledgment in a representative capacity: State of Washington. A Washington notary acknowledgment form is used to officially authenticate a signature on a legal document.The Washington Notary Acknowledgement form is a legal document that confirms a signer's identity and willingness to sign a particular document. The Washington Notary Acknowledgement forms are documents used to prove the validity of a signature on a legal document. 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. The short-form acknowledgment certificate is used when an individual is signing and acknowledging on his or her own behalf.