If you clear and start over, then you can just import anew from the 2016 return. But the fact is, you are starting your 2017 return from scratch. You really have no other choice unless you want to spend the time manually entering everything. Either way, you're spending the time. If you're not starting your 2017 taxes over from scratch and re-importing all from 2016, then you are manually having to enter everything that would have otherwise been imported from the 2016 return. The choice is yours. But if you don't clear and start over and re-import everything, if you make a mistake on your manually entry of the otherwise imported data, it will come back to bite you a few years down the road, and instead of costing you time, it will cost you $money$.
