In Lin v. Unemployment Compensation Board of Review, 558 Pa. 94, 735 A.2d 697 (1999), the Supreme Court considered whether a private postage meter mark was sufficient to establish the date of filing of an appeal from a UC service center's notice of determination. At that time, the timeliness for appealing such a decision was controlled by Section 101.82(d), which stated that the filing date of a mailed appeal "shall be determined from the postmark appearing upon the envelope in which the appeal form or written communication was mailed." Lin, 558 Pa. at 97, 735 A.2d at 698-99 (quoting 34 Pa. Code 101.82(d)). Regarding whether, under this regulation, the date of filing could be determined by a private postage meter mark, the Court stated: We have held several times that a private postage meter mark is not the equivalent of an official U.S. Postal Service mark, and is not determinative of the timeliness of an appeal. We have also recently held that the "regulation 34 Pa. Code 101.82(d) as drafted does not recognize placing an appeal in the mail as the initiation of the appeal. The regulation recognizes only the postmark date . . . ." The U.S. postmark, as opposed to a private meter postmark or testimony concerning the placing of the appeal in the mail box, is virtually unassailable evidence of the time of mailing of an appeal. Accordingly, we hold that when the envelope containing the appeal does not have an official U.S. postmark, it must be deemed filed when received. We agree with the Commonwealth Court that a United States postmark is the most reliable means of accurately dating the mailing of an appeal in an unemployment compensation case. The date on a private postage meter can be readily changed to any date by the user; therefore it lacks the inherent reliability of the official United States postmark. Accordingly we concur with the Commonwealth Court that an appeal in unemployment compensation matters bearing a private postage meter mark should be considered filed when received. Hence, the appeals filed in the instant cases were untimely as the envelopes bore private postage meter marks and were received after the filing deadline. Lin, 558 Pa. at 98-100, 735 A.2d at 699-700.