Notarial Acts, Acknowledgments, and Jurats
The two certificates candidates confuse
An acknowledgment proves that the signer appeared, was identified, and acknowledged executing the document voluntarily for its stated purpose. The signature itself may have been made earlier; the notary is certifying the acknowledgment, not the signing. Typical wording: 'Acknowledged before me on [date] by [name].'
A jurat proves something different: that the signer signed the document in the notary's presence and swore or affirmed that its contents are true. The notary must actually watch the signature and must administer the oath. Typical wording: 'Subscribed and sworn to (or affirmed) before me on [date] by [name].'
An oath or affirmation without a document is a separate act; an affirmation is used when a person objects to swearing, and it has the same legal effect as an oath.
Accuracy rules
The date on the certificate must be the actual date of the notarial act - never pre-dated, never back-dated. The notary signs the name as commissioned and applies the seal. If a person cannot sign, a signature by mark may be notarized as usual, with the mark witnessed as the circumstances require.
Rule of thumb
Ask two questions. Is the signer swearing to the truth of the contents? Then it is a jurat, and the notary must witness the signature. Is the signer only acknowledging a signature already made? Then it is an acknowledgment.
Worked example
A signer brings a completed affidavit, already signed, and says 'I swear this is true.' The notary cannot convert it into a valid jurat without seeing the signature. The notary should have the signer re-sign in the notary's presence, administer the oath, then complete the jurat.