Md. Code, Tax - General § 7.5–301

(a) Except as provided in subsection (b) of this section, each person required to file a return under § 7.5–201 of this title shall pay the digital advertising gross revenues tax with the return that covers the period for which the tax is due.

(b) A person required to file estimated digital advertising gross revenues tax returns under § 7.5–201(b) of this title shall pay:

(1) at least 25% of the estimated digital advertising gross revenues tax shown on the declaration or amended declaration for a taxable year:

(i) with the declaration or amended declaration that covers the year; and

(ii) with each quarterly return for that year; and

(2) any unpaid digital advertising gross revenues tax for the year shown on the person’s return that covers that year with the return.