I had a similar concern with not just Coinbase, but with several accounts on other exchanges. If you only have taxable crypto transactions on your Coinbase account then you should use the cointracker.io service for connecting your transaction history to turbotax. A cointracker.io account is free for coinbase users and it should link directly with your Turbotax Premier account. Half of this I learned from just online research, so I haven't been able to successfully complete all of my crypto tax stuff because I am using Turbotax Home and Business.
