You can find the invoices to Virtuagym in the business settings under license and invoices. Here you find a complete overview of your invoices, outstanding and paid. You can also download the invoices here for your administration.
Please note that the invoices you create for your clients (if you have the membership and billing package) are found in a different app, called "financial".
If you want to know which actions increase the price of your license, check out this article.