Md. Code, Tax - General § 13–603

(a) Except as otherwise provided in this section, if a claim for refund under § 13-901(a)(1) or (2) or (d)(1)(i) or (2) of this title is approved, the tax collector shall pay interest on the refund from the 45th day after the claim is filed in the manner required in Subtitle 9 of this title to the date on which the refund is paid.

(b) A tax collector may not pay interest on a refund if the claim for refund is:

(1) made under any provision other than § 13-901(a)(1) or (2) or (d)(1)(i) or (2) of this title;

(2) based on:

(i) an error or mistake of the claimant not attributable to the State or a unit of the State government;

(ii) withholding excess income tax;

(iii) an overpayment of estimated financial institution franchise tax or estimated income tax; or

(iv) an overpayment of Maryland estate tax based on an inheritance tax payment made after payment of Maryland estate tax; or

(3) made for Maryland estate tax or Maryland generation-skipping transfer tax more than 1 year after the event on which the claim is based.