Whenever payment of all or any portion of the tax imposed by this article is required to be received by the Department on or before a certain date, the taxpayer shall be deemed to have complied with this article if the letter transmitting payment of such tax is received by the Department and is postmarked by the United States Postal Service on or prior to the final day on which the payment is required to be received. Any private postage meter or similar device imprinting a postmark or date shall not be controlling upon the Department.
61 Pa. Code § 119.28