While some states don’t legally require a Notary to use a seal, they can add authenticity and professionalism to a document.
In the absence of a seal, states often require that the Notary’s name, title and commission expiration date be stamped, typed or printed in ink that can be photocopied near the signature of the Notary. A seal can accomplish this in states that require it, and even in non-seal states, redundancy of this information in a seal still has value.
For example, if you’re notarizing a document that’s going out of state, it could be challenged or questioned in a state that requires seals.