If you used the TurboTax desktop CD/Download editions installed on your personal computer to complete the 2016 tax return and this year you are going to use the TurboTax online editions for 2017 then you will need to transfer the 2016 tax data to the online 2017 tax return.

See this TurboTax support FAQ for transferring the data from a computer to the online editions - https://ttlc.intuit.com/questions/3006086-can-i-transfer-a-2016-turbotax-return-from-my-computer-to-...

If you used the TurboTax online editions to complete the 2016 tax return then you only have to start the 2017 online account using the exact same user ID you used to create the 2016 online account.