Whenever any payment, statement, report, or other communication received by the Office of Finance is received after the time prescribed by this chapter for the receipt thereof, but is in an envelope bearing the postmark showing that it was mailed prior to the time prescribed in this chapter for the receipt thereof, or whenever the Office of Finance is furnished substantial proof that the payment, statement, report, request, or other communication was, in fact, deposited in the United States mail prior to the time prescribed for receipt thereof, the Office of Finance shall regard such payment, statement, report, request, or other communication as having been received on time.