How do I file for my 3rd stimulus never received

[xmasbaby0]

You do not "file" for the 3rd stimulus.  There is no place to enter anything about the 3rd stimulus check on a 2020 tax return.

TurboTax cannot track your 3rd stimulus or tell you when it will arrive.  The IRS is issuing 3rd stimulus checks on its own timetable.

You can use the IRS Get My Payment site to see what is expected for your 3rd stimulus check:

https://www.irs.gov/coronavirus/get-my-payment

https://www.irs.gov/coronavirus/get-my-payment-frequently-asked-questions

[Critter-3]

If you did not get a third stimulus based off the 2019 return then file a 2020 return to  get the third stimulus issued.   If you did file the 2020 return then all you can do is wait for the IRS to process the 2020 return and issue any third stimulus payment you are eligible for  and if you don't get it in advance then the only option left is to apply for the credit on the 2021 return you file next year. 

[SweetieJean]

The IRS is sending out Stimulus #3 is batches, and will continue to do so for several more weeks.