40 Pa. Stat. § 1187
Every member of, or subscriber to, a rating organization shall adhere to the filings made on its behalf by such organization except that any such insurer may file with the Commissioner a uniform percentage decrease or increase to be applied to the premiums produced by the rating system so filed for a kind of insurance, or for a class of insurance which is found by the Commissioner to be a proper rating unit for the application of such uniform percentage decrease or increase, or for a subdivision of a kind of insurance (1) comprised of a group of manual classifications which is treated as a separate unit for rate making purposes, or (2) for which separate expense provisions are included in the filings of the rating organization. Such deviation filing shall specify the basis for the modification and shall be accompanied by the data upon which the applicant relies. A copy of the filing and data shall be sent simultaneously to such rating organization. Any such deviation filing shall be on file for a waiting period of thirty (30) days before it becomes effective, unless the Commissioner reviews and authorizes the filing to become effective before the expiration of such period, and shall be subject to the provisions of section five. Each deviation shall be effective for a period of not less than one (1) year from the date such deviation is filed unless terminated sooner with the approval of the Commissioner or in accordance with the provisions of section five.
40 P.S. § 1187