NEW YORK (CNNMoney.com) -- Americans are drowning in credit card debt - over $5,000 on average. And credit card companies aren't helping the situation.

A recent study by the Government Accountability Office found that credit card companies do a poor job disclosing fees. In today's tips we're going to tell you what you need to know about fees and disclosures.

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Fees are everywhere! And according to the GAO report, they might not be disclosed.

Here are some fees you need to look out for: Fees for making payments over the phone, fees for balance transfers, fees for increasing your credit line, over-limit fees and cash-advance fees. They can range from $10 to over $30.

And penalties are far stiffer than they were in the past. Late fees have more than doubled in the past 10 years. And if you miss a payment - even by a few hours - your interest rate could increase to 30%, according to Curtis Arnold of cardratings.com.

By law, all those credit card offers must have a disclosure box that lists the annual percentage rate, finance charges and annual fees. But what you want to know is what triggers a late charge or whether the credit card company has a universal default clause that raises your interest rate if you miss a car payment or you're late on a mortgage payment.

If you're shopping around and you need that info, you'll need the Card Member Agreement details. Make sure you call the customer service line and ask questions about the specific details of the card.

If you have a corporate credit card, your personal credit may still be on the hook. Late fees on company cards can lower your credit score and bump up the interest rate on other cards - even if it's your company that is late paying the bill, according to Ed Mierzwinski of the U.S. Public Interest Research Group.

Sixty percent of Federal employees and 23% of private sector employees have corporate cards, says Rick Palmer of Eastern Illinois University who has studied this issue. Bottom line is that you're name is on the card, so may be on the hook.

First, find out if your corporate card is listed on your credit report. Then you'll need to find out what your company's policy is when it comes to payment. Of course make sure you file your expense reports with plenty of time to spare.

Just a note of caution here: credit card companies are trying to encourage you to use plastic to pay for small transactions - like coffee or a magazine - by not requiring a signature on payments less than $25.

Keep in mind that this is not a good idea since it's often hard to remember all the "little purchases" that can really add up at the end of the month.

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