There is no such thing as a “general certificate.” A notarial certificate must match the notarial act being performed. Depending on your state, the available certificate options may include an acknowledgment, jurat, or signature witnessing certificate.
If your document does not include a notarial certificate, the notary may describe the available certificate options, but the signer must choose the notarial act they want performed. Once the signer makes their selection, the notary may attach the appropriate certificate and proceed according to state law.