Parent alert! Does your child have a Social Security card? If not, you'd better get one soon. Under the new tax law, almost every child 5 and older has to have a Social Security number.

The new law requires that you list the Social Security number of any child (age 5 and older) who you claim as a dependent on your federal income tax return. There's a $5 fine if you don't or if you report the number incorrectly.

So far, about 2.2 million children have received their cards, according to John Trollinger at the Social Security Administration. Between now and tax-filing time, another 4.8 million are expected to apply.

Right now, the process takes about two weeks -- and Social Security thinks it can keep to that schedule, even in a crunch. I'd guess, however, that by next March the waiting time could be a lot longer.

Why does Uncle Sam want your child to have a number? The idea evolved from an IRS tax-evasion study.

One way people have cheated is by claiming a dependent they don't really have. After a divorce, it has not been uncommon for each parent to take an exemption for the same child.

In 1982, the number of exemptions for absent kiddies was estimated at 8 million, says the IRS, up from 2.7 million in 1965. The congressional solution? Require Social Security numbers on tax returns.

If divorced parents each claim the same child, the IRS computer can now discover it by cross-checking numbers. And although some crafty taxpayers supposedly have gotten Social Security cards for their dogs, the new law at least makes it harder to claim a nonexistent child.

But those taxpayers might argue that a $5 fine is a small price to pay for an undeserved exemption worth $1,900 in 1987.

Does a missing Social Security number increase your chance of being audited? Here's the circumspect answer from the IRS's Rod Young: "There will be a penalty for each number that's missing or incorrect. We wouldn't go ahead and disallow the exemption. But if the return were subject to audit and the taxpayer couldn't verify the dependency, the exemption would be disallowed."

Yes, Rod, but what about the audit?

"Well," he went on, "the criteria for an audit aren't public and a variety of factors will make your score add up to a significant number. Not just one factor. We may also just send out notices to people asking them to supply the missing numbers."

Got that?

Here's how to get your child a Social Security number -- either through the mail or in person:

Get the application form from your local Social Security office, read the instructions and fill it in.

Send original documents (or, if lost, copies certified by the original issuer) to prove your child's age, citizenship and identity.

Normally, Social Security requires a birth certificate plus a separate document proving identity: a school ID card, a day care record, a passport, a vaccination certificate, a Girl Scout membership card. If you can't think of one, call the local office and ask for suggestions. (The phone number is listed under U.S. Government.)

If your child is too young to sign his or her name and you apply for the card in person, you also have to send proof of your own identity -- like your voter registration card, insurance policy, church-membership record, passport or work badge.

This applies to the parent or other legal guardian. But such proof isn't necessary if you apply by mail, according to Helen Harvey of the Social Security Administration.

A person age 18 or older who has never had a Social Security number has to apply in person rather than by mail.

What if Social Security loses your original documents?

"What can I say?" Trollinger sighs. "We take every precaution. ... But if they're lost, people will have to replace them themselves."

What if you pay no attention to this column and apply so late that the number doesn't come by April 15? Just write "applied for" in the space where your child's Social Security number should go. It might save you a $5 fine. This time.