When a notary public's authentication is required, a notarized certificate must be ready to go. This usually requires the presence of the person requesting the notarization, who must sign the certificate in front of the notary. The notary then certifies the identity of the signer and that they willingly signed the paper. The particular circumstances in which a notarized certificate is necessary may differ depending on local laws and regulations, as well as the nature of the document or transaction in question. Legal documents, real estate deals, affidavits, and some corporate agreements are some common instances.