In order to generate your license key, you'll need to register your Amazon purchase.
Your Amazon order number will be included in the email receipt Amazon sent:
You can also find your YNAB/Amazon order number in your Amazon account:
1. Go to Amazon.com
2. Click on "Your Account".
3. Click on the "Your Orders" button.
4. Find your order number on the left side, listed under the date of the order.