The "12-month rule" refers to United States tax guidelines established by the Internal Revenue Service regarding travel tax-free stipends. Under these regulations, a travel nurse can receive tax-free money for housing and meals only if they are temporarily working away from their permanent tax home. If a travel nurse accepts assignments in the exact same metropolitan area or facility for more than 12 months out of any consecutive 24-month period, the IRS considers that location their permanent tax home, rendering all subsequent stipends fully taxable income.