Maryland Code, Local Government § 4-409

(a) At any time within 45 days after enactment of an annexation resolution, at least 20% of the qualified voters of the municipality may petition the chief executive and administrative officer of the municipality in writing for a referendum on the resolution.

(b) After a petition is presented to the chief executive and administrative officer, the officer shall verify:

(c) After verifying compliance with the requirements of this section, the chief executive and administrative officer, by proclamation, shall suspend the effectiveness of the annexation resolution pending the results of the referendum.