You can verify if you've sent the invoice by going to the Activities section, ap_quinn.
Aside from this, you'll also know if they have viewed the invoice. I'll show you how:
Through the Activities section:
With regards to the Bcc email, it's possible that you have not turned on the Email me a copy option. Let me guide you with these steps:
If you want to let your clients pay the invoices online, you can add a Pay now button. Feel free to check out this article for more information about the process: Create an invoice your customer can pay online.
There you have it, ap_quinn. Thanks for dropping by!