CLEVELAND, Ohio -- New consumer-friendly rules taking effect today will mean colossal changes for the 180 million people nationwide who have credit cards -- and even millions who don't.

If you pay with plastic:

No longer will banks arbitrarily be able to change the interest rate on your balance.

No longer can they confuse you by changing the date your monthly payment is due.

No longer can they cut your credit limit, allow you to go over it, then charge a penalty.

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And the list goes on. But even the half of the population that doesn't carry credit debt could feel the impact of the changes. To make up the money the new rules will cost them, banks are expected to impose new fees on credit cards, and even on checking accounts and debit cards.

The credit card changes are so extensive that it seems difficult to believe they're all happening at the same time. Any one of them would be a big deal. Congress approved the overhaul last spring.

The reform is the biggest to hit the industry since the credit card was invented 60 years ago, said Kenneth Clayton, senior vice president and general counsel at the American Bankers Association. "It's the opening of a new age."

Said Jay Seaton, president of Consumer Credit Counseling Service of Northeast Ohio: "Credit cards are going back to the way they worked 20 years ago. You buy something, you pay the bill. There won't be all of this 'gotcha.' "

Here's a look at some of the changes that take effect Monday:

Some other changes

Here's what else credit card companies must do, or can't do, under the new law:

Must give you 45 days' notice before changing your rate on future purchases, changing your fees or making other major changes.

Can't charge fees for payments made by phone or online, unless it's a last-minute payment with expedited handling to avoid a late fee.

Must allow you to opt out of account changes and pay off existing balances within five years.

Must apply payments first to the highest-rate balances.

Can't issue cards with upfront fees exceeding 25 percent of available credit.

Can't raise your rate if you fall behind on payments to another creditor.

Can't increase your rate on new purchases for the first year of opening a card.

Must mail statements 21 days before due date.

Other changes:

Companies that offer free credit reports must disclose that they're not the official free credit report available by federal law and must direct people to annualcreditreport.com

Regulators will study issues such as credit profiling of cardholders based on the stores where they shop.

-- Teresa Dixon Murray

Interest rates can't be raised on existing balances.

In the past, the interest rate on your balance could be changed pretty much at the blink of an eye. On a $9,000 balance, the $75 a month you paid in finance charges at 10 percent jumped to $217 a month if your rate was raised to 29 percent.

There was nothing you could do about it except pay off the card or transfer the balance. Now, rates can't be raised on existing balances unless you're more than two months behind on payments or you had a teaser rate that expired. However, if your rate is tied to an index rate, such as prime rate, then your rate can increase by the same number of points the index rises.

Consumer advocate Adam Levin, chairman of Credit.com, believes this could be the most important change. There was just something inherently wrong with getting people to borrow money, then changing the terms, said Levin, former director of the New Jersey division of consumer affairs. "This is one of the things that made people the craziest."

Due dates must be the same every month.

Keeping track of credit card payment due dates was often like watching a racquetball game -- the dates could jump from the 20th to the 12th to the 16th and back again.

Now, the due date must be the same every month -- the 10th, the 15th or whatever. If that date falls on a weekend or a holiday, then the next business day is the due date.

Payments are on time if received by 5 p.m. on the due date.

Many companies imposed late fees for payments not posted by 10 a.m. or even 7 a.m. No more.

Firms can't charge overlimit fees without your permission.

Going over your credit limit isn't a good thing. But it's painful when going over the limit by $1 costs $39, or when one mistake costs more than $100, as multiple fees add up. That can't happen anymore.

Unless you ask your credit card company to allow you to go over your limit, transactions that exceed the limit may be denied. You won't be charged a fee. If you do go over your limit, you'll be charged a penalty fee only once per cycle, not once for every purchase over your limit.

No more two-cycle billing.

Many companies have charged interest based on a customer's average daily balance over the past two months, not just the average balance from the most recent month. That means you were essentially paying interest twice on some purchases. Now, interest will be figured only on your last month's average daily balance.

Minimum payment disclosures.

Consumers' credit card statements must contain information on how long it will take to pay off their bill if they make only the minimum payment, and how much it will cost long-term.

No marketing to college kids.

Companies won't be allowed to promote credit cards on college campuses or to send pre-screened card approval letters to anyone under 21.

Even if young adults hear about credit cards through other sources, they won't be able to open an account unless they can document they have income to repay the debt. Otherwise, they'll need a cosigner.

Jerry Welch, chief executive office of nFinanSe Inc. of Florida, whose company sells reloadable debit cards, expects an explosion in his business, in part from young adults who will have difficulty getting credit cards. The college population alone is 18 million, he said.

Of course, all of these changes will cost the industry dearly in interest charges and fees. Just how much is a matter of speculation, said Clayton of the American Bankers Association in a conference call.

Seventy percent of credit card companies' revenue comes from interest charges, 20 percent from merchant fees and 10 percent from consumer fees. Penalty fees alone -- such as overlimit or late-payment fees -- yielded $15 billion to $20 billion last year, the federal government says.

All of this means credit card companies will have to change their business models, primarily by taking less risk and by finding other ways to get revenue.

Consumers have already seen cards canceled and credit limits lowered. Now they will find it more difficult to get new accounts, too, said Nessa Feddis, vice president and senior counsel at the American Bankers Association, in a conference call.

Those who do have cards -- people with bad and good credit alike -- can expect to pay higher rates on new transactions, since banks won't be able to raise rates on existing balances. Credit card issuers also are slicing rewards and launching new fees.

Annual fees have returned, and some banks such as Citibank are charging fees if you don't use your card enough. And you'll see increases in fees still allowed, such as for balance transfers, Seaton of Consumer Credit Counseling predicts.

Look for people without credit cards to feel the effects, too, said Jean Ann Fox, director of financial services for the Consumer Federation of America. She expects some banks to impose checking account overdraft fees by not posting deposits until after all withdrawals have been subtracted each day. And she predicts a surge in banks' pushing cash advances on checking accounts, with interest rates exceeding 100 percent.

Levin of Credit.com noted that credit card companies can still make some changes to accounts with 45 days' notice. To sneak those changes past consumers, some companies have been experimenting with making envelopes look as much like junk mail as possible, he said -- so watch your mailbox closely.

"You have to remember, these companies aren't making these changes because they wanted to," he said. "They've been dragged kicking and screaming, and they're not really happy about it."