Whatever you may think about the immigration law that President Reagan signed last November 6, don't ignore it. Enforcement of the law is starting in earnest.

To keep illegal aliens from finding work in the United States, the new law and regulations require most employers to check the documents of all new hires -- including that recent engineering-school graduate born and raised in Topeka, Kans. To be sure, the law wasn't conceived as a slap at employers, but it is nonetheless a triple hit. You have to keep more records, your hiring and labor costs may rise, and you risk being caught up in conflicting regulations. Paperwork violations could cost you thousands in fines. And there are criminal penalties for certain repeat offenders -- up to six months in prison.

You could shrug your shoulders and figure the law isn't going to affect you since you've never hired illegal aliens -- or any foreigners. But even if all your new hires are U.S. citizens, just forgetting to check their papers makes you a lawbreaker. And beware: a law that is unreasonable or impractical, which I find this one to be, invites arbitrary, uncertain, and therefore unfair enforcement. Congress has appropriated more than $400 million a year for enforcement during 1987 and 1988. Some of the money will go for more border patrols, but the major new thrust is to crack down on employers. To this end, the Immigration and Naturalization Service (INS) is hiring additional enforcement officers, and the Department of Justice has set up a special prosecutor's office.

Cathie Shattuck, a labor and employment lawyer with Epstein Becker Borsody & Green, in Washington, D.C., thinks it likely that the INS will focus enforcement efforts on certain industries: the garment industry, construction, restaurants, hotels, and other businesses that traditionally rely on significant numbers of illegal immigrants. But she cautions that activity initiated by the INS will be only one prong of the enforcement effort. The Department of Labor, for instance, in the course of routine wage-and-hour audits, will begin reporting questionable records to the INS.

While some kinks in the law will no doubt be worked out over the next few months, your best bet for now is to get the documentation required by law. You must determine two things about the people you've hired since November 6, 1986 (unless they left your employment before June 1, 1987, or unless they're referred to you by a state employment agency that documents their eligibility to work). You must verify that they are who they say they are, so you need something that confirms their identity; and you have to determine that they are legally entitled to work in the United States.

This may be tougher than it sounds. U.S. citizens, of course, are eligible to work here. But so are many noncitizens. Permanent resident aliens, for example, can work wherever they want. Others, such as representatives of international organizations, can work only for the employer who brought them over. Certain foreigners who have applied to become permanent resident aliens can work here for a limited time. Although the INS has issued detailed guidelines, it is up to you to know whether the forms that job applicants present entitle them to work in the United States. Take this responsibility seriously. If you discriminate against foreigners who are eligible to work here -- by arbitrarily denying them jobs -- you could be penalized.

Use your common sense and good judgment to decide if an applicant's papers seem authentic -- not forged. You don't have to investigate any further. But be sure to notice any limitations, such as expiration dates. While you might be within your rights to hire people initially, you could be prosecuted for keeping them on your payroll after their eligibility expires. And be on the lookout for temporary work authorizations issued before June 1, 1987, which expire after June 1, 1988. If one of your employees has such a document, he or she will have to get it updated after June 1, 1988, or you'll face penalties by having that person on your payroll.

Despite the added paperwork and expense, you should probably keep on file photocopies of the papers proving that your new hires are entitled to work in the United States. While the law doesn't require this, the INS recommends that you do so to protect yourself against possible INS prosecution.

The new immigration law has stringent time limits and few exceptions. You have to verify employees' eligibility within 3 days after hiring, unless they have lost the documentation, or haven't gotten it yet. In this case, they have 3 days to give you a receipt showing that they've applied for the document and 21 days to produce it. What do you do if the documents don't show up? If you can hold up on your hiring, avoid this problem by making your job offers contingent upon getting the proper documentation. When all else fails, ask the INS for guidance. You also should turn to the INS if documents arrive but are annotated with restrictions you don't understand.

Remember, too, that you don't have to check papers for employees you hired before November 6, 1986, even if you know they are in the country without legal authorization. And if any employees hired after that date tell you they don't have a document that entitles them to work, but that they are seeking legalization, don't fire them. The new law provides amnesty under which certain illegal immigrants have until September 1 to produce appropriate documents.

Don't accept any job applicant's offer to reimburse you for any penalties you may incur if he or she doesn't produce acceptable papers. Similarly, don't require an employee to reimburse you if you're fined. It's illegal. You could be fined up to $1,000 for each violation, and you'll have to return any money you've collected.

After you've checked an employee's papers, you sign a new INS form, the I-9, which notes what you've reviewed and records your conclusion that a new employee is legally entitled to work in the United States. You don't have to do this for independent contractors. But you must fill in an I-9 even if an employee comes from an employment agency that has already checked documents and filled out an I-9 for the applicant. You must keep every I-9 for at least three years or until a year after the new employee leaves your company, whichever is longer. So far, there's no word on whether you can store I-9s on microfiche or in some other more convenient and less bulky way.

As with many other tasks a law imposes, you can pay an outside service to verify documentation and fill out I-9s, but you remain liable for seeing that the law is satisfied. And if you sign an I-9 that you know contains any untrue statements, you could be subject to penalties for perjury.

The INS may enter your offices without a subpoena to look at your I-9s. You have three days to produce them, and if you don't, the INS can fine you up to $1,000 for each employee hired after November 6, 1986. Penalties are stiffer if it's found you've hired illegal immigrants. The INS or an administrative-law judge can order changes in your hiring practices to assure that you don't hire any more of them.

The INS can also fine you up to $2,000 for each illegal immigrant hired after November 6, 1986. A second violation means fines up to $5,000 for each illegal immigrant, and for subsequent violations, up to $10,000.

You must respond to an INS charge that you've violated the law within 30 days. You should specifically ask for a hearing; otherwise, the INS may have the right to assess a fine.

To avoid running afoul of the new immigration law and save yourself from the most confusing paperwork, it may seem sensible to hire only people who look and sound like native-born Americans. But if you have at least four employees, you could then be prosecuted for discrimination, since many U.S. citizens may appear "foreign," and many foreign-born people are entitled to work here. The best advice is to ignore nationality or citizenship when you are evaluating job applicants and to be consistent in the way you treat each of them.

If you are found guilty of discrimination, you could be ordered to hire the applicant and give him or her up to two years' back pay. In addition, you may have to pay a penalty of up to $1,000 for each person you discriminated against. The Department of Justice can also require that you keep extra records for up to three years, so they can ensure that you're no longer discriminating against job applicants.

Ironically, the immigration law makes you vulnerable to a variety of discrimination charges. For instance, while the law says you could be jailed for discriminating against certain foreigners, it allows you to favor Americans in some circumstances -- if, for instance, a U.S. citizen and a legal immigrant are equally qualified for a job. But what if both are more than adequately qualified for the job? Who should you choose?

There's another potential trap: many civil-rights laws forbid you to hire, promote, or fire someone because of age or nationality, and in some states it's illegal to ask for this information on job applications. Yet the new immigration law requires this data on the I-9 form. To protect yourself, make sure you use the I-9 only to determine whether a person is legally entitled to work in the United States and not for any other hiring decision. It's probably a good idea to store the forms in a secure file away from other personnel documents. Don't enter information from the I-9, such as age and citizenship, into a general company database. The fewer people who have access to I-9s, the less likely the documents can be used to sustain a claim that you discriminate because of age, citizenship, or national origin.

In the months ahead, the regulations will no doubt evolve as the INS, courts, and employers wrestle to interpret the new law case by case. My advice is to keep your eyes on the INS.