The IRS has for years reassured undocumented workers that their tax information is confidential and that it is safe for them to file income tax returns without fear of being deported. About half — possibly more — of the roughly 11 million undocumented immigrants in the country file income tax returns to document their payments to the U.S. government, according to researchers.

“It is a complete betrayal of 30 years of the government telling immigrants to file their taxes,” one former IRS official said, speaking on the condition of anonymity out of fear of retribution.