Sunset Clause

A sunset clause is a clause that will expire and no longer be in effect as of a specific date unless action is taken to extend the period of effectiveness.

Example:

The legislature included a sunset clause to a bill passed in 2016 that would automatically adjust the gas tax rate for inflation so that it would increase or decrease on its own until June 30, 2019. If the experiment is successful then they will extend it an additional 5 years.