Declares that the notice of intent to commence a medical malpractice action shall be given by regular mail, registered mail, or certified mail with return receipt requested, by depositing the notice, with postage prepaid, in the post office addressed to the defendant.

Provides that if the defendant is a health care provider entity or, at the time of the alleged professional negligence, was acting as an actual agent or employee of such a health care provider entity, the notice may be addressed to the chief executive officer, administrator, office of risk management, if any, or registered agent for service of process, if any, of such health care provider entity. Notice for a claim against a local government entity shall be filed with the agent as identified in RCW 4.96.020(2).

Allows the claimant to have an additional five court days to commence the action when the ninety-day extension expires.