Can I get 3rd stimulus money for new dependent when ex claimed him last year

My ex-mother-in-law had my 16 year old last year for 7 months and claimed him on her 2020 taxes but he moved in with me in August 2020. I want to know how I  can get the 3rd stimulus and on for him. We really need the money right now I don’t wanna have to wait till the 2021 tax season

Get your taxes done using TurboTax

unfortunately, it doesn't work that way.

 

the 3rd stimulus is an advance credit against the 2021 tax return.  The only way to get the $1400 is 

 

1) wait on the stimulus payment from the IRS.  You can't apply for it.

2) Obtain the Recovery Credit on the 2021 tax return.