After you file

NO such date has been mentioned ... if your 2018 return has DD information on it then they will be sending out payments by DD over the next 2 weeks ... if your money gets sent before you file the 2019 return you will need to wait for the 2020 filing next Jan to reconcile the credit ... if you did not get enough in advance you can get more later.

Per the IRS: https://www.irs.gov/coronavirus/economic-impact-payments