53 Pa. C.S. § 8847
(a) General rule.--Except as provided in subsection (b), for purposes of taxation, if there is a change in assessment made by the board as a result of an assessment appeal, a taxing district shall apply the changed assessment in computing taxes imposed in the next fiscal year of the taxing district following the fiscal year in which the board heard the appeal and rendered its decision.
(b) Exceptions.--Subsection (a) shall not apply to:
(1) Interim assessments made pursuant to section 8841(c)(relating to assessment roll and interim revisions).
(2) Reductions in assessments due to a catastrophic loss pursuant to section 8815 (relating to catastrophic loss).
(3) Correction to assessments made due to clerical or mathematical errors pursuant to section 8816 (relating to clerical and mathematical errors).
53 Pa.C.S. § 8847