The mutual 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, and the funds earned by each kind of insurance shall be kept separate and shall not be available to pay losses or expenses incurred by any other kind of insurance; provided, that 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.