At the end of a billing cycle or at the time you make a purchase and incur a one-time fee, AWS charges the payment method you have and issues your invoice as a PDF file. You can view these invoices through the AWS console, which will show summary information of all usage and cost incurred for that one off item, or billing period.
Log into the console via SSO and go to the billing dashboard:
Select Orders and invoices from the menu on the left:
Click on an Invoice ID corresponding to the month you wish to view:
It will download a PDF version of your invoice similar to below: