Again, this is just a repeated work around causing an extra step to remember, more time, and still losing money on every transaction. 

Personally I think it is unprofessional and tacky to ask a customer how they plan to pay. Frankly, as long as they pay their bill so I can pay the employees it's really none of my business how they want to pay, and they may not know right there on the spot if they will write a check or pay with their bank or credit card, so now they're on the spot rather than privately making that decision. If I send out an invoice for a customer to pay, here are the options:

(1) I send it out with no credit card fee, and turn off credit card payment for this invoice. They can still pay with a check or bank with no fee, but if they do want to pay with CC then they have to reach out and ask me to turn it back on and add on the fee. Which can delay payment time if I cannot get back to them right away, especially if they are traveling or out of cell service.

(2) I send it out with the credit card payment turned on and the credit card fee added. Then if they do not pay with a credit card they either have to calculate their payment themselves or reach out and have the charge removed, or worse, they do not notice the line on the invoice or assume it will only be charged if they do use a credit card, and now I have unprofessionally over-charged the customer. 

Plus, once the customer pays the invoice, if the charge is forgotten, there is no way to submit a second charge to the payment method or add the charge before it batches to cover the fee, it would have to be invoiced separately, which is again, unprofessional and tacky.