Section 4518. Amounts credited on life insurance certificates

Any
  individual life insurance certificate may provide that  in  addition  to
  any  minimum  benefits guaranteed in the certificate, additional amounts
  may be credited to the certificate. No such additional amounts shall  be
  guaranteed   or  credited  except  upon  reasonable  assumptions  as  to
  investment income, mortality, persistency and expenses. The  declaration
  of  such  additional amounts by a society must be made prospectively; no
  such additional amounts shall be credited retroactively to apply to  any
  period  prior  to  such  declaration.  No  such  additional  amounts are
  required to be credited to any certificate with respect  to  the  period
  after  the termination or lapse of such certificate by reason of default
  in payment of any premium, installment or interest  on  any  certificate
  loan  and  before  the  reinstatement  of  such  certificate,  if  it is
  reinstated. Any such additional amounts shall be  credited  on  a  basis
  equitable to all certificate holders of a given class and shall be based
  on written criteria approved by the board of directors of the society or
  a committee thereof.