If you would like to authorize someone to use your credit card, here is a sample template you can use to write a credit card authorization letter.
(Bank Name and Address)
Subject: Credit Card Authorization
I, (Name) would like to authorize (Authorized Name) to use my credit card for transactions that he/she deems appropriate. I request you to please allow (Authorized Name) to use my credit card from the letter’s date till (End-Date).
Please find the details of my card below.
Credit Card Number:
Please let me know if you have any questions.