To view your Invoices, first visit the 'Account' tab of the Account Dashboard and then click the 'Invoices' button in the top toolbar.You will be taken to a page that will list all your paid invoices (and a $0 invoice for your trial period, if applicable).
Here is a guide to View your Invoices / Receipts:
https://www.quiz-maker.com/Quiz-Help/Invoices