When does a notary signature need a witness?

A notary signature typically requires a witness when the state law mandates it for specific types of documents, such as wills or certain real estate transactions. Additionally, if the signing parties request a witness for added verification or if the notary believes it adds to the document's validity, a witness may be included. It's essential to check the specific requirements of the state where the notarization is taking place, as laws can vary.