40 Pa. Stat. § 1227
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 deviation from the class rates, schedules, rating plans or rules, respecting any kind of insurance, or class of risk within a kind of insurance, or combination thereof. Such deviation filing shall specify the basis for the modification and a copy thereof shall also be sent simultaneously to such rating organization. Any such deviation filing shall be on file for a waiting period of thirty 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 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. § 1227