Did you import any W2 or 1099? Then you might have also manually entered it. That can happen. If you import a 1099 it may also import another 1099 you weren't expecting then you manually entered the other 1099. What line on your 1040 is doubled? Be sure to always review your return before you file. Make sure you understand each line on your return. If you don't then post questions.
Before filing, You can preview the 1040 or print the whole return
https://ttlc.intuit.com/community/accessing/help/how-do-i-preview-my-turbotax-online-return-before-f...
