A will requires the signature of two witnesses, over 18 years old, who actually see the person making the will sign the will. It also requires a notary's attestation that the witnesses and the person making the will were present and identified when the will was signed. The same is true for a living trust.
RCW 11.12.020 does not require that a Will be Notarized to be valid. The statute states that the will must be in writing and signed by the Testator. The will must also be signed by two witnesses who are in the presence of the Testator when they sign as witnesses. It is a common practice in Washington to complete a "Self Proving Affidavit" at the same time a Will is signed. Unless this affidavit is also attached to the Will, the court in a probate proceeding may require that the witnesses to the Will provide an affidavit stating they witnessed the will and at the time of execution they believed the testator had capacity to execute the document. This is where the Notary comes in to play.
Similarly it is good practice to have signatures of the Trustor and Trustee notarized at the end of an express Living Trust.
In Washington, a Will need not be notarized. It must be signed by 2 witnesses in the presence of the decedent. In order to enter the Will into probate in court, you will need testimony from the 2 witnesses. This can be submitted via an affidavit signed by the witnesses. If the affidavit of the witnesses is attached to the will at the time of the testator’s execution, it is considered a self-proving Will. If the decedent’s Will is signed by two witnesses, but is not self-proving, in order to prove the Will, you will need to obtain affidavits from the two witnesses to the Will. Pursuant to GR13, RCW 9A.72.085, and Estate of Starkel, 134 Wn.App. 364, 134 P.3d 1197 (2006) the requirement of an affidavit is fulfilled by a declaration signed by the witnesses. A declaration need not be notarized. The declaration may be substantially in the following form: “I certify (or declare) under penalty of perjury under the laws of the State of Washington that the foregoing is true and correct.” Estate of Starkel, 134 Wn.App. 373. The declaration must state the place of execution and date the declaration was executed.