40 Pa. Stat. § 91
In determining the liabilities upon its contracts of insurance of any insurance company, other than life insurance companies, and the amount such company should hold as an unearned premium liability, the Insurance Commissioner shall calculate such amount on a monthly pro-rata basis or its equivalent on the premiums in force at the end of any quarterly or annual period, except in the case of noncancellable health and accident insurance issued on and after January first, one thousand nine hundred fifty such amount shall be calculated according to the methods set out in section 311.1 of this act : on perpetual insurance, he shall charge the cash deposit received, less a surrender charge of not exceeding ten per centum thereof. For marine and inland insurance, he shall charge fifty per centum of the premium written in the policy upon risks covering more than one passage not terminated, and the full amount of the premium written in the policy upon all other marine and inland risks not terminated: Provided, That the Insurance Commissioner may, in his discretion, charge a premium reserve equal to the unearned portions of the gross premiums charged, computed on each respective risk from the date of the issuance of the policy.
40 P.S. § 91