Compare both returns line by line to see any differences. If you filed with TurboTax last year, you should also have a two year comparison.
Where do I access the side by side comparison of two years
TurboTax has a "Two-Year Comparison" report that compares 2018 and 2019.
For TurboTax Online users, you can find that report if you "Print, Preview, or View a PDF" of you tax return with all the worksheets. That Two-Year Comparison "lays 2018 and 2019 side by side". To print or preview a PDF of your return with all the worksheets before you file, select Tax Tools and then Print Center from the left menu, and then select the first option, Print, save, or preview this year's return and follow any additional instructions.
You can find the Two-Year Comparison in Forms mode (icon top right in blue bar) if you are using a Download/CD version of TurboTax. When you click the Open Form button, be sure to include the hyphen in your search for Two-Year Comparison.