How do you write a letter to give permission to sibling to sell your car?

To write a letter granting permission to your sibling to sell your car, start by addressing the letter to your sibling and clearly stating your intent. Include your full name, your sibling's name, the details of the car (make, model, VIN), and a statement that you authorize them to sell it on your behalf. Sign and date the letter to validate it. You may also want to include your contact information for any further inquiries.