Force Client Login When Paying Invoices

I issue credits to my VIP clients and I rely on Spiro to deduct them automatically; however, I discovered today that the credits don’t get deducted unless the agent logs in to pay. One of my agents just clicked Pay Invoice in the auto-sent email, never logged in, and was charged the full amount instead of the discounted amount. The bigger problem caused was having to issue a partial refund instead of a whole refund. I’d like to keep this from happening again by making it so that Spiro forces the agent to login prior to payment OR making it so the agent doesn’t have to login in order for the credit deduction to work. Thanks!!