I rent studio space to artists and am trying to move to automated billing wherever possible. I have a question regarding using their card saved on file:

I have a client who is renting one weekend a month over the course of the year. I set up invoices for each of the dates--they are not strictly regularly occurring, so the due dates and amounts vary somewhat. I usually set up my recurring invoices to send an e-mail 5 days before the billing date, so they have some warning of the upcoming charge; but this doesn't appear to be an option on one-off invoices, so be it. But here's the issue right now:

She paid her first month's bill and saved her credit card on file as instructed. I now have a stack of future invoices due on various dates: one in a month, another in two months, three months, etc. I want her to receive e-mail notifications on the day she is invoiced, letting her know her card is being charged.

Now that she has a card on file, I went into the next invoice that will be due and chose her card from the drop-down, expecting it to simply bill her on the date specified on the invoice. Instead, the "Send" button in the upper right corner changed to "Charge", which to me implies she will be charged right now today, but the invoice isn't actually due until the end of the month. I don't want to have to personally go to each and every invoice on the due date and trigger the payment--that moves the onus on me instead of an automated process I thought this would offer.

Is the button change simply a misleading UI behavior? Will the billing actually occur on the date I set, or today when I choose her credit card as the billing method?