Whether or not a person qualifies is based upon their 2019 reported income so if you had a significant drop in 2020 income you could be outa luck for a check.
Close.
Whether you get one and how much is based on your 2019 tax return AGI.
If you haven't filed your 2019 taxes, then it is based on your 2018 return AGI.
If you made more than $75k filing singly or $150k filing jointly on your 2018 return, but made a lot less in 2019 you want to file your taxes ASAP to get a bigger benefit. If you made less than $75k singly, $150k jointly in 2018 then it makes no difference either way, you should get the full $1200 for single filers, $2400 for joint filers, and $500 per dependent child (if you have any)