A Twin Cities woman failed to pay income taxes for many years in connection with her family excavation and sewage treatment business, saying she and her husband are not U.S. citizens but permanent residents of the “Kingdom of Heaven,” according to federal charges.

In an indictment unsealed Friday in federal court in Minneapolis, Tami M. May, of Anoka, was charged with obstruction of due administration of IRS laws and 15 counts of filing false tax returns.

May remains free on a $25,000 bond. Reached Monday by phone, her husband, Dennis, declined to comment.

The Mays operate D & T & Son Excavating in Coon Rapids. According to the indictment and prosecutors, they did not file income tax returns or pay income tax from 1998 until 2005, despite receiving payments from customers totaling hundreds of thousands of dollars.

In April 2005, the IRS notified Dennis May that he owed taxes for 2003, plus penalties and interest. After that, Tami May made numerous “obstructive and fraudulent filings with the IRS including filing frivolous ‘zero income tax returns.’ ”

She also claimed that she and her husband were not U.S. citizens but permanent residents of the “Kingdom of Heaven” in an attempt to claim hundreds of thousands of dollars in fraudulent income tax refunds, authorities said. Dennis May has not been charged; the U.S. attorney’s office declined to say whether he would be.