When you amend the 2020 and put that you are not eligible to be a dependent and that you did not get the first two payments, then 1,800 will be added to your refund. But the third payment is an advance on 2021 income taxes so will not be claimed on 2020 return.
Amend will be available in TurboTax in late March. Do not attempt to amend until the function is available. It is best to wait until your current return has been processed before filing an amend.
You generally must file an amended return within three years of the date you filed the original return or within two years after the date you paid the tax, whichever is later.
