Many gas stations have a policy of charging more for using a credit card versus paying with cash. The price differences are clearly marked at the pump, and consumers have the right to choose whether or not they will pay a little extra for the convenience of using plastic. What if that policy was the case on every purchase you made? As of January 27, that became a distinct possibility, as terms of a settlement between credit card companies and merchants.

Last July, these two parties agreed to a settlement that would allow merchants to add on surcharges to cover the cost of processing a credit card transaction. While the surcharge would vary depending on how much the merchant has to pay in processing fees, it could mean that you might pay up to an additional four percent on your purchase.

While on the surface this might look like a tough nut to swallow, this settlement may not have that much of an effect on consumers. For starters, debit cards are not included in this settlement, so consumers can continue to pay with those types of cards and not worry about paying additional fees.

Secondly, this settlement doesn't apply to American Express cards because the card's contract with merchants stipulates that they can't add any surcharges to customer tabs.

Thirdly, ten states also forbid merchants from adding credit card fees onto retail purchases, so if you live in one of the following states, this issue will not affect you: California, Colorado, Connecticut, Florida, Kansas, Maine, Massachusetts, New York, Oklahoma and Texas.

Merchants also can't be sneaky about levying this charge. If a merchant plans on implementing a credit card surcharge fee, the law stipulates that it must disclose this activity clearly by posting informational notices at check out. E-commerce merchants must post a notice about the surcharge on their websites and do so on the page that first mentions they offer the ability to pay with credit cards. For both in person and online transactions, purchase receipts must clearly break out the surcharge fee.

With mobile payments becoming more available, merchants can also tack on the surcharge to transactions paid for with smart phones or mobile devices. Again, the merchant must clearly inform the consumer about the surcharge fee before the point of purchase.

In all three cases, merchants must also clearly note the fee amount on receipts, whether they are electronic or paper.

The actual amount of this surcharge will vary depending on the agreement a merchant has with the card company. Most card fees range between 1.5 to 3 percent of the purchase price. The maximum surcharge allowed is 4 percent. Stores are only allowed to pass the swipe fees onto their customers; they cannot earn any additional monies from these surcharges.

Although retailers are now allowed to utilize this fee, they aren't mandated to do so. Whether or not retailers will actually do it is yet to be seen. According to watchdog group Consumer Action, some retailers already build the cost of credit card swipe fees into their everyday prices, so they may opt not to use the surcharge option. Other retailers may not wish to add on the fees in fear of losing customers and will freely continue offering the convenience of paying with credit.

Consumers don't necessarily have to put up with paying for the surcharges either. Consumer Action says that consumers can ask for a discount, if they believe the retailer has already set item prices to include what they'd pay in surcharge fees. Consumers also still have the option of using a debit card, should they want to pay with plastic. And, they can always pay with cold, hard cash.