A favorite IRS trick is to request its victim's banker to freeze his account, and surrender its contents after 21 days if he has not satisfied the IRS. Accompanying the letter is a copy of 26 USC 6331 (d), which says:

Levy may be made under subsection (a) upon the salary or wages or other property of any person with respect to any unpaid tax only after the Secretary has notified such person in writing of his intention to make such levy.
Such third-party levies never include a copy of subsection (a) to which this refers, yet subsection (a) begins:
If any person liable to pay any tax neglects or refuses to pay the same within 10 days after notice and demand, it shall be lawful for the Secretary to collect such tax (and such further sum as shall be sufficient to cover the expenses of the levy) by levy upon all property and rights to property (except such property as is exempt under section 6334) belonging to such person or on which there is a lien provided in this chapter for the payment of such tax. Levy may be made upon the accrued salary or wages of any officer, employee, or elected official, of the United States...