Are you used to getting a fat envelope from your bank with all your canceled checks? Well, soon those checks may not be in the mail.

In case you haven't heard, the Check Clearing for the 21st Century Act -- Check 21 for short -- is scheduled to take effect on Oct. 28. Basically, the new law allows banks to replace paper checks with digital copies of the originals. Currently, after most checks are deposited they have to be transported across town or across the country to the originating bank before they can be cleared.

Under Check 21, banks will be able to create digital copies of the front and back of your checks and electronically transmit the information through the banking system. That means checks could clear in hours instead of days.

For many people the new law won't change how they do banking. Check 21 does not require banks to send or accept checks electronically and many won't do so for a while.

However, many bank customers (59 percent) already have their checks withheld from their statement and use images to prove they paid for something, according to the American Bankers Association (ABA).

I was surprised to learn that only 36 percent of Americans still receive their original checks with their statements, according to a telephone poll of 1,000 consumers conducted in January for the ABA.

Still, Check 21 may be difficult to accept among elderly consumers, many of whom still get their canceled checks in the mail. According to the ABA poll, 50 percent of consumers 55 and older get their checks back. Only 23 percent of consumers between the ages of 18 and 34 do.

But that brings me to another question: Do you float?

Have you ever paid a bill or written a check when you knew you didn't have the money in your checking account?

Oh, you were sure it would be there by the time the check cleared. So you played the float -- the time it takes for your check to clear.

With the implementation of Check 21, banks will be able to quickly debit your accounts for checks you write, but they won't be under any obligation to speed up the crediting of checks that you deposit into your accounts. This hardly seems fair, consumer groups say.

Consumers Union and the Consumer Federation of America are concerned that banking customers who rely on the float will get flooded with bounced-check fees. In fact, with faster check processing, the check you write at Wal-Mart could clear by the time you get home from the store.

The two consumer advocacy groups say that by mid-2005, banking customers could be bouncing almost 7 million more checks and paying an additional $170 million in fees each month.

The groups have launched an online petition to put pressure on banks to adopt a set of consumer safeguards for the new law. For example, they are urging banks to help consumers get used to this new law by suspending bounced-check fees during the first two months after Check 21 takes effect.

Consumers can sign the online petition in support of the safeguards at the Consumers Union Web site.

But may I be blunt? If you're playing the float as a regular money-management strategy, it means you aren't managing your funds well.

You should know better than to write a check if you don't have the money in your account. Bounced-check fees (or a nonsufficient fund fee, as banks call it) are no joke these days. The fee averages about $25 per bounced check.

So why encourage bad banking behavior by suggesting banks suspend bounced-check fees?

"We're asking for a grace period because some people may think that if their checks are clearing faster then the checks they deposit will be cleared fast, too," said Gail Hillebrand, senior attorney with Consumer Union's West Coast office. "We are looking at a behavior that may not have been wise but was not costly in the past. Now it's going to be expensive."

Consumers Union and Consumer Federation of America are also urging banks not to charge consumers for "substitute checks."

A substitute check is a paper copy of the digital image of your original check -- both front and back. All banks must accept the substitute check as proof of payment as they would the original document.

The ABA says images of checks have been accepted as proof of payment by the courts and the IRS for decades. But Hillebrand said that to be safe, if you're currently receiving just copies of your checks or online images, ask your bank if it will provide you with a legal substitute check upon request and, if so, will there be a charge.

Some banks charge for substitute checks, while others don't.

Look, there are a lot of nuisances about Check 21, but the law also contains a number of new consumer protections. For example, bank customers are entitled to a special expedited refund if their account is debited incorrectly because of a substitute check.

If you write checks, read up on this new law. For more information, read the fact sheet that the consumer groups have prepared at http://www.consumersunion.org/finance/ckclear1002.htm.

I would also encourage you to read the fact sheet prepared by the Federal Reserve Board at http://www.federalreserve.gov/check21/faqs.htm.

Researcher Lorraine Denis-Cooper contributed to this column.

Michelle Singletary discusses personal finance Tuesdays on NPR's "Day to Day" and online at www.npr.org. Readers can write to her at The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or by e-mail at singletarym@washpost.com. Comments and questions are welcome, but please note that they may be used in a future column, with the writer's name, unless a specific request to do otherwise is indicated.