Last week, when I realized I hadn’t paid my GM Visa card, and the payment was due within two days, I called their handy 800 number, and was invited to pay my bill with the assistance of their helpful operator, Mike – for a $15 fee. This is an industry standard, referred to as a “convenience fee.” I wasn’t even late and they were already trying to extract money from me just for paying my bill, which isn’t really convenient at all when you think about it.

Mike was kind enough to tell me if I signed up on their Web site, I could pay my bill online (thus avoiding the inconvenient convenience fee), but I had to do it within the hour, or the payment wouldn’t be received in time. Even an electronic payment, he claimed, could take a full two days to reach them. Did I believe that? Of course not. But they make the rules and we have to follow them or pay the consequences.

Take my friend Joel, a tap dancer, who debuted on Broadway tapping in the last revival of "42nd Street," then went on tour with “The Producers.” He was, he says, making pretty good money as a swing (the industry term for someone who covers all the chorus tracks), but when it came to his credit cards, he was more of a juggler than a dancer.

"I’m always juggling between three bank cards," says the tapper. And, admits Joel, it’s a lot to keep track of – with all those payments, he’s sometimes late sending in the monthly minimum. Worse still, if you’re late even once, most cards will instantly rescind the great transfer deal percentage rate and have the right to raise your annual percentage rate (but more on that in a moment).

Last year, the average late-payment fee rose 3 percent to $29, marking the largest increase in the industry's history, according to CardWeb.com, which tracks and publishes information on credit cards. But more and more issuers, including Citibank, Discover, Fleet and MBNA now charge tardy customers a flat $35, regardless of the customer’s balance.

Also gone are the days when issuers allowed 10-15 days for a payment to arrive after a due date before charging a late fee. You've got to be on time with that card payment; if your payment arrives even one day late you'll be punished. As noted above, if you’re paying electronically, you may think you’re sending in your payment in the most expeditious fashion, when in fact, it may not “get there” for a full day.

To make matters even more confusing, some issuers have early morning posting times. Say your bill is due at 6 a.m. on its due date. If your payment arrives with the 9 a.m. mail on the day it's due, it can be considered late.

"It's part of the strategy of trying to figure out how to get more people to pay more money," observes Deirdre Cummings, consumer program director at Massachusetts Public Interest Research Group, which released a survey of 100 credit-card offers.

More for Them, Less for Us

Consumers who regularly shuffle their debt from one card to the another – which accounts for most of us – are finding their actions are a growing source of revenue for the issuers.

A 4 percent fee on a $1,000 balance would cost $40. Some issuers cap fees at $150.

Last month, Joel was offered an excellent 1.99 percent transfer rate to move $2,500 from one card to another, only to find out they charged him an additional $77 to make the transaction.

“Seemed like a lot just to take my money,” said the dancer.

The difference between the interest rate you signed on for and your new penalty rate can be considerable. Say you qualify for Capital One's so-called no-hassle platinum card, with a fixed rate of 8.9 percent, carry a balance of $4,000 and pay $200 monthly. If you pay late twice in six months, your rate will go to 19.8 percent. This means it will take you two additional months to pay down your debt and cost you $796, or more than twice as much, in finance fees. Other cards will impose the rate hike with just one late payment.

Selective Terms for Select Customers

Most consumers don’t know that card issuers tailor their terms to fit individual customer profiles. Those with stellar credit qualify for the best rates, while those with spotty credit pay a premium. In fact, the range of interest rates paid by individuals is broader than it has ever been, with post-teaser rates ranging from 4.75 percent to 35 percent, according to CardWeb.com.

Even if you do qualify for a low rate, you must be on your best behavior to keep it.

According to a survey by the advocacy group Consumer Action, nearly 70 percent of all issuers said they would raise a customer's rate for paying late. Some issuers have taken this a step further and will raise rates if they see any change in your creditworthiness. This means that paying late on one credit card could also affect your rate on an entirely different card.

When informed of this possibility, Joel just shrugged: "I’m tapping as fast as I can."