legal tender for all debts, public and private

https://www.consumerfinance.gov/ask-cfpb/what-is-a-convenience-fee-or-pay-to-pay-fee-en-2126/

They can charge fees, as long as there is an alternate way to pay without a fee. Usually it's by check in the mail.

Now that they gotten us to accept a fee, sooner or later they'll jack up the fee. It's only $2 now, but in a few years, it will be $5, and then $10, and you better pay it if you want your lights to stay on.

And politicians will help them do it by passing a law that the fee can't by larger than the actual payment, or some helpful horseshit like that.

There are several gas stations who offer a cash price that is about 10 cents a gallon cheaper than the credit card price.

Yeah, we really need laws defending the right to get discounts for low fee payment methods. I should pay less for using my debit card than someone using a credit card that charges a fee to the seller (which is passed on to all customers) that's high enough to give them back 1+% of what they spend. And a further discount for cash

That's because every credit card swipe carries a fee of about 2.75%, and that comes out of company profit, so they are recouping that fee. They want you to pay for the processing fee, not them.

As near as I can tell, it's still free to send them a paper check, and that has to be the most expensive form of processing, and the least convenient for them, so send a check, and really piss them off.