Md. Code, Insurance § 3–305

A report, affidavit, or return that must be filed under this subtitle complies with the filing requirement if the report, affidavit, or return is:

(1) mailed and postmarked by the United States Postal Service on or before the filing date;

(2) delivered on or before the filing date to a private delivery service recognized by the Commissioner, if the delivery is evidenced by a receipt; or

(3) transmitted electronically on or before the filing date in a manner approved by the Commissioner.