I give them a separate paper receipt(invoice), and email them the credit receipt. I have had a few old fuckers make me print one out at the office for them. I use squareup because it's the first major reputable company. When my bank comes out with one, I'll probably switch.
I've only used Google voice for personal forwarding, but I don't think what you're trying to do would be an issue.
I've only used Google voice for personal forwarding, but I don't think what you're trying to do would be an issue.