The main purpose of this legislation is to modify the Earned Income Credit (EIC) under the Internal Revenue Code. Specifically, it aims to create a permanent lookback provision that allows taxpayers to use their previous year's earned income when calculating their EIC if their current year's income is lower. This change is intended to provide more financial support to low- and moderate-income families during times when their income may fluctuate. Key provisions of this legislation include the establishment of a lookback option for taxpayers.