Using a merchant account is a bad idea, if you are using one in place its a bad idea as if they find out you would get shutdown and would place problems for legit transactions. Its not advisable to open a merchant account for this purpose also, as it is against the TOS.


I dont get the official payments idea as where are you going to send the 100k, if your tax bill is that high I think you aren't going to be too worried about buying miles via rewards. I think there are fines for overpaying taxes by an excessive amount.

Also overpaying an AMEX can get them to freeze your account, they do not like it when you overpay its a giant red flag for illegal activity.