Whenever a filing is submitted by an insurer to the Insurance Commissioner to revise the rates or supplementary rate information applicable to any policy subject to the provisions of sections 38a-663 to 38a-696, inclusive, the filing shall specify an effective date, provided the filing may specify separate effective dates for new business and renewal business. Such rates or supplementary rate information shall only apply to policies with an inception, continuation, or renewal effective date on or after the appropriate filing effective date, regardless of the date the policy is written, issued, processed or delivered. If either a coverage is changed or an exposure is added during the policy period, the insurer shall specify, at the time of the original filing, whether the applicable rates will be (1) the rates in effect at the beginning of the policy period, or (2) the rates in effect on the effective date of the change in coverage or the addition in exposure. If the latter rates are specified, such rates shall apply only to the changed coverage or the added exposure.