You assume that the IRS is actually looking for such things so that they can prosecute them. And while that may be true for us citizens, IRS rules specifically prohibit its agents from notifying immigration if they suspect they may be dealing with illegals. Under IRS rules, illegals who have been in the country long enough to meet residency rules are considered to be resident aliens. "Although the immigration laws of the United States refer to aliens as immigrants, nonimmigrants, and undocumented (illegal) aliens, the tax laws of the United States refer only to RESIDENT and NONRESIDENT ALIENS... Under these rules, even an undocumented (illegal) alien under the immigration laws who passes the Substantial Presence Test will be treated for tax purposes as a RESIDENT ALIEN," (Introduction to Residency Under U.S. Tax Law). Federal law and IRS rules specifically prohibit the IRS and its agents from sharing information with other government agencies - including immigration. They don't want the threat of possible deportation to interfere with their ability to collect tax dollars. As long as you are paying taxes, or claiming to, the IRS doesn't care if your are here legally or not, which is why the IRS will issue ITINs (individual taxpayer identification numbers, initially issued to legal resident aliens who could not legally obtain a social security number but still had tax liabilities here in the US) to illegals. And if all of those refunds go to one address, oh well, that's just the way it is. They are forbidden from notifying any other federal agency - and probably wouldn't even if they could.