Taxpayers who has significantly lower income in 2020 than in 2019 may want to file their 2020 tax returns as soon as possible if the 2020 return could result in a larger stimulus payment this year.

USA Today has a good overview of the issues:

https://www.usatoday.com/story/money/taxes/2021/02/23/tax-return-stimulus-check-file-early-dependents/4552270001/