40 Pa. Stat. § 917
A mutual insurance company, other than a mutual life company, shall maintain unearned premium and other reserves separately, for each kind of insurance, upon the same basis as that required of domestic stock insurance companies transacting the same kind of insurance, except that the Insurance Commissioner may, by written order, fix a different basis of reserve for losses and claim in workmen's compensation insurance. Any reserve for losses or claims based upon the premium income shall be computed upon the net premium income, after deducting any so-called dividend or premium returned or credited to the member. The provisions relating to unearned premium reserve shall not apply to policies issued by a domestic mutual fire insurance company under the authority of section 202(b)(1), which policies set forth therein, or in the promissory note attached thereto, a limited or unlimited liability to assessment. Such companies shall accumulate such reserves not later than December 31, 1976.
40 P.S. § 917