For the stimulus check, I have filed my 2019 taxes and they’ve been accepted but I had a child of this year of 2020. Will the IRS know I have a child for the additional $500 you get?

[bluedeb · Accepted solution]

No, you cannot claim a child born in 2020 on a 2019 return.  The IRS is only using information from a 2019 return (or 2018 return if no 2019 return was filed).  You will qualify for your dependent when you file your 2020 return.