The main purpose of this legislation, known as the Working Families Disaster Tax Relief Act, is to provide financial relief to taxpayers who have been affected by disasters. Specifically, it allows these individuals to use their earned income from the previous year to qualify for certain tax credits, namely the earned income credit and the refundable portion of the child tax credit. This change aims to help those who may have lost income due to disasters by allowing them to base their eligibility for these credits on a more stable financial year.