How do you write authorization letter for proxy of witness marriage?

To write an authorization letter for a proxy witness at a marriage, include the date, your name, and your address at the top. Clearly state your intent to designate a proxy, including the name and address of the proxy witness. Specify the date and location of the marriage ceremony, and include a statement affirming your consent for the proxy to act on your behalf. Finally, sign the letter and consider having it notarized if required by local laws.