7 Pa. Code § 137b.92 – Time period within which roll-back taxes are to be calculated and notice mailed.

(a) General. A county assessor shall calculate the roll-back taxes and interest, and mail notice of these roll-back taxes to the affected landowner, within 5 days of learning of a change in status triggering liability for roll-back taxes. The county assessor shall also mail a copy of the notice to the other taxing bodies of the district in which the land is located.
(b) Notice of change of application. If a county assessor receives a ‘‘notice of change of application’’ described in § 137b.63 (relating to notice of change of application), and that notice triggers liability for roll-back taxes, the 5-day period described in subsection (a) shall commence as of receipt of that notice.