Chief among the reasons to have certain documents notarized is that having a document notarized is a deterrent to fraud. Getting agreements notarized adds a layer of verification. Notarization is the assurance by a duly appointed and impartial Notary Public that a document is authentic, that its signature is genuine, and that its signer acted without duress or intimidation, and intended the terms of the document to be in full force and effect.
Notarization not only makes it more likely that signors are who they say they are but also is mandatory in some states for certain agreements, such as deeds, mortgages, easements, powers of attorney and living wills.
Having certain papers notarized also is important when disputes are litigated; affidavits, which are sworn statements, will not be considered by a court unless they are notarized. Notarized documents also are considered self-authenticating, which means the signers do not need to testify in court to verify the authenticity of their signatures.