Maryland Code, Land Use § 18-209

(b)(1) If the revenues from the taxes are inadequate to pay the principal of and interest on the bonds, the county guaranteeing the bonds shall impose, in each year the taxes are inadequate, an additional tax on all assessable property in the portion of the metropolitan district in that county sufficient to make up the deficiency.

(2) If the revenues from the additional tax under paragraph (1) of this subsection are inadequate, the county shall impose a tax on all assessable property in the corporate limits of the county sufficient to pay the deficiency in the revenues available to pay the principal of and interest on the bonds.