https://taxfoundation.org/federal-coronavirus-relief-bill-cares-act/#0
The rebates are tax credits that will be applied to 2020 tax returns, but are advanced to taxpayers now based on their 2019 or 2018 adjusted gross income (AGI). The credit will be applied to 2020 tax returns using 2020’s AGI next spring, and taxpayers will receive the difference of the credit if it is in their favor.