Idaho Code § 59-1315: Amount, terms and conditions of revised benefits are to be prospective only unless otherwise provided.

As the amount, terms and conditions of benefits may be revised from time to time the application of such revisions shall be prospective only and not retrospective or retroactive unless otherwise provided by statute. Accordingly, unless otherwise provided, a member’s benefits are determined based upon the terms of the plan on the date of the member’s last contribution as an active member.