10 Things Credit Card Companies Don't Want You To Know. Part 6 0f 10

April has been Credit Card Question and Answer month here at Financial Elite. We continue with Part 6 with information provided from an article from SmartMoney about the little known rules that are costing you money and putting your credit, your identity and your family at risk.

Banks generally calculate interest charges in one of two ways: based on average daily balance or on something called two-cycle billing. The latter, which more card issuers are not adoption, penalizes consumers who carry a balance, even if it's only on occasion.

Here's how it works: Say you start your month with a zero balance and charge an amount that you don't pay off in full at the end of the month. If your card uses the average daily balance method to calculate interest, you are charged nothing for the month you made the purchase and interest only for subsequent months in which payment is outstanding. With two-cycle billing, interest charges begin with the day you make the purchase.

Banks defend two-cycle billing as correcting the true interest charges for credit card purchases. Ron Brooks, a spokesman for National City, says it's a way to make sure card users pay interest should they suddenly go from being transactors (those who pay every month) to revolvers (those who carry a balance).

One way to avoid the issue is to stay away from credit cards that use two-cycle billing to calculate interest charges and stuck with those that go by average daily balance. Unfortunately, it's not a permanent solution. Your card provider can switch between the two with just a 15 day notice, so you'll have to keep checking.