Another issue would be the time needed to validate employees who are erroneously found to be ineligible for work, Aitken said. Such errors can result from something as simple as transposed digits in Social Security numbers, problems with hyphenated names, and name changes resulting from marriages, he said.

Aitken's organization sent a letter raising those issues to Senate , on Wednesday. Also backing the SHRM's position are the National Association of Manufacturers, Association of American Universities and the HR Policy Association.

According to the DHS' own about 96% of employees are work-authorized within 24 hours, while about 4% receive initial mismatches. Less than one-half of a percent of those mismatches are later confirmed to be authorized to work, meaning the system is generally reliable in spotting mismatches.