Maryland Election Law Section 13-322

      A campaign finance report is timely if:

            (1)      regardless of when it is received, the United States Postal Service has affixed a mark on the envelope or on a receipt verifying that the campaign finance report was mailed on or before the filing deadline; or

            (2)      it is received by the State Board or the local board with which it is required to be filed within 3 days after the filing deadline and a private postal meter postmark or a receipt by a private carrier verifies that the campaign finance report was mailed or delivered to the private carrier on or before the filing deadline.