If you would like to authorize a joint bank account holder to operate your account, here is a sample temperature can use to write a joint bank account authorization letter.
(Bank Name and Address)
Subject: Joint Bank Account Authorization Letter
To Whomsoever It May Concern
I, (Your Name), am writing this authorization letter to request you to transfer my ownership over my bank account to (Authorized Person). As I cannot handle and take care of my financial needs alone, I would like (Authorized Name) to take action on my behalf whenever required.
Please find the attachments of the authorized person’s documents with this letter and let me know if you have any questions.
(Your name and Signature)