For years, educated credit card holders have been safe in the knowledge that a merchant could not require them to purchase a minimum amount in order to charge something to their cards. But with the recent passing of the finance bill, the door has been opened to allow such minimums — and the card companies are just fine with that.

Visa is leading the way in this brave new world of minimum charges. Consumerist reader Pete recently noticed that on the card company’s site, it now reads, “U.S. retailers may require a minimum purchase amount on credit card transactions. The minimum purchase amount must not exceed $10 and does not apply to transactions made with a debit card.”

To see if the other card companies were following suit, we checked out the info available on their sites.

In the American Express Merchant Manual [PDF], Section 3.2 says Merchant may not: “impose any restrictions, conditions, disadvantages or fees when the Card is accepted that are not imposed equally on all Other Payment Products, except for ACH funds transfer, cash, and checks.”

To us, this implies that — so long as the merchant requires the same minimums on all the other cards it accepts, AMEX is okay with it too.

We checked with a rep for AMEX who confirmed:

American Express’ policy has been to require parity with other payment products (this is the “equally imposed” section you referenced). In other words, if a merchant chooses to require a minimum for credit card transactions – it must be the same for all credit card products. As you’re probably aware, the Dodd-Frank Act allows for merchants to set $10.00 minimums for credit card transactions but does not allow merchants to differentiate by issuers or payment card networks (i.e. a minimum for a card issued by Bank X on Network Y but not cards issued by Bank A on Network B).

And then we looked at the MasterCard site and had a glimmer of hope when we stumbled upon Rule 5.11.3 in its Merchant Guide [PDF]. It reads:

“A Merchant must not require, or indicate that it requires, a minimum or maximum Transaction amount to accept a valid and properly presented Card.”

Alas, our hopes were dashed when we reached MasterCard for comment on the Visa rule change and received the following reply:

“MasterCard will be modifying its rule similarly in the near future.”

We tried to locate rules for the Discover card and were fruitless in our search. Additionally, no one at Discover has responded to our request for comment.

What do you think of the credit card companies allowing merchants to require minimum charges? Do you expect to see more merchants posting notices of $10 minimums?