Thank you for your question!
Amazon makes it pretty easy to de-register a device. In order to do that, follow these steps:
To deregister a device:
- From the Amazon website, go to Manage Your Content and Devices.
- Login with your Amazon account credentials.
- Click Devices.
- Select Deregister.
As a reminder, when disposing of any devices (or selling them), make sure to deregister those devices ahead of time so no one can use them to access your account or make purchases!
Hope that helps you!