Credit Card Balance Pay Off: This truth starts to matter when you decide to pay off all your debt and realize that it's harder to get to zero than you thought.

Even if you pay off your entire balance, as listed in plain black print on your statement, you may still be socked with interest in the month after you supposedly got rid of your debt.

Know the terms.  The credit-card issuer has pertinent advice for consumers -- read the terms.

If you are assessed interest after you pay off a balance,  call the issuer to see if it can possibly be lifted.

If you pay online, you still have to be careful to get the exact amount you owe. A quick check of a few credit-card sites revealed that the online "payoff balance" isn't totally correct, either. You still have to make the call and ask for a calculation to get your up-to-the-minute balance.

Other traps
Sometimes, it's not just residual interest that's making it hard for you to payoff credit card balances, even when you think you're writing a check for the full amount.

The double billing cycle. In other words, the cycle is 60 days, not 30 days. Credit card companies are doing this to, in essence, penalize those that repay and to garner greater interest over a greater period.

Credit card companies are changing the terms of credit agreements to increase their ability to collect interest. The bottom line is that it's all legal if they tell you. And the last thing those tiny letters want to do is make it easy for you to payoff the balance in full.

Your best defense, according to both issuers and personal finance experts, is to read very carefully -- and call with pointed questions -- to make sure zero really means zero.