2019 returns are not due until 7/15/2020 or extended ones to 10/15/2020.  TPC’s estimates assume that all of those eligible for a payment receive one. However, it is likely that some will not, perhaps because they did not file a tax return or receive a Social Security benefit in 2019. Even though the payment could be based on 2018 or 2020 income tax returns for those who did not file in 2019, there still will be some who may not get payments, perhaps because they did not file returns for those years, are unbanked, or may have moved.

If you haven't filed federal taxes for 2018, do that right now

The IRS said if you haven't filed your 2018 federal taxes, that could affect your stimulus check and recommends that anyone who hasn't filed a 2018 tax return to file now.