In some cases, if your income in 2019 qualified you for more EIC than your 2020 income, you had the choice of using your 2019 income to calculate your EIC. Turbotax would have asked you something like "It looks like you might qualify for earned income credit. Would you like to try to see if your 2019 income would give you a larger credit?" If you said yes, then the program walked you through the calculation and you already submitted a tax return with the best possible claim.
If you said "no" (or if you ignored the question and it defaulted to no) then is is possible that recalculating your EIC would result in a larger credit. If so, you can file an amended return. But, it may not make a difference, depending on your total situation. You would open your tax file, start the amending process, and re-run the EIC interview, paying attention to all the questions. You may need to manually copy in some information from your 2019 return, so have a copy nearby when you start the amending process.
