Maryland Code, Local Government § 20-127

(a) Except as provided in subsection (b) of this section, a tax imposed under this title may not be collected after 7 years from the date the tax is due.

(b) If a tax collector fails to collect a tax and a receiver or trustee is appointed within the period specified in subsection (a) of this section to complete the tax collection, the period for collecting the tax extends for 2 years from the date that the trustee or receiver is appointed.