Md. Code, Insurance § 6–106

(a) Each person subject to taxation under this subtitle shall make a declaration of its estimated tax if the person’s total tax for the current taxable year reasonably is expected to exceed $1,000.

(b) A person required to make a declaration of estimated tax shall:

(1) file with the Commissioner:

(i) an initial declaration of estimated tax on or before April 15 of the taxable year; and

(ii) a quarterly estimated tax report on or before June 15, September 15, and December 15 after filing the initial declaration; and

(2) pay to the Commissioner at least 25% of the tax estimated for the full taxable year with the initial declaration for that year and with each quarterly report for that year.