72 Pa. Stat. § 5452.15
At least thirty (30) days' written notice shall be given to any taxable person whose assessment shall be changed at any triennial assessment, or between triennial assessments, in a manner which would mean an increase in the taxes on such real estate if the same tax rate should prevail setting forth any change which has been made and the time and place set for hearing objections thereto. At least thirty (30) days' written notice shall also be given to any taxable person if the established predetermined ratio is changed within the county.
Any required notice shall be served by the board or any member thereof or by any assessor or by any other person authorized so to do by the board upon said taxable person or may be mailed to him or her at his or her last known address by first class mail.
When no service is made upon the taxable person by an authorized person or by first class mail, said notice shall be deemed to have been properly served if tacked or conspicuously posted upon the property assessed.
No defect in service of any such notice of an assessment change shall be sufficient ground for setting aside any assessment so made, but upon proof thereof being made, the taxable person shall have the right to a rehearing before the board relative to said assessment and to appeal therefrom to the court of common pleas as hereinafter provided.
72 P.S. § 5452.15