Efforts to have employers check the Social Security numbers of potential workers in a federal database may sound simple. Think again.

Like many efforts to stem illegal immigration, this one is fraught with unintended complications.

Rep. Dennis Moore, a Kansas Democrat, is among the sponsors of the New Employee Verification Act, which seeks to have every new employee in the United States checked by the federal E-Verify system.

That’s about 55 million checks each year. Some say the estimated cost to implement the law could be more than $10 billion.

E-Verify is a free, Internet-based data system that allows employers to check the validity of prospective employees’ Social Security numbers. More than 65,000 employers are using the program, which the Department of Homeland Security oversees.

E-Verify has improved since its beginning in 1997. Two strong enhancements announced this month are records of legal immigrants who have become naturalized U.S. citizens, and reference checks with border inspection records that could show the work authorization of immigrants who have recently legally entered the country.

But E-Verify is often still unable to flag stolen Social Security numbers because it cannot distinguish duplicate users of the same number. Critics also have pointed out mistakes in the database that could result in legal workers being denied employment.

Another concern is that employers will avoid hiring Hispanics in an attempt to dodge being fined or questioned by federal or state officials. That would unfairly limit job opportunities for many applicants.

New layers bureaucracy often unintentionally create a wider black market for people attempting to skirt new rules.

Illegal immigrants once purchased fraudulent documents with fake Social Security numbers to gain employment. Increasingly, escaping detection requires valid numbers.

So identity theft grows, harming more innocent individuals whose numbers are stolen.
Unfortunately, it is possible for an illegal immigrant to pass an E-Verify check, and the person whose identity has been stolen never knows.

Comprehensive immigration reform is needed. In the absence of that, these piecemeal actions can only go so far.