It depends on what you have on your return. If you have something like carry forwards (Tuition, losses), RRSP contributions or something else that affects multiples years, then what you did in 2016 will affect your 2017 return.

If you do file your 2017 return and then find out you need to make a change based on your 2016 return, you can always make an adjustment.

To make adjustments on a tax return that has already been filed: https://turbotax.community.intuit.ca/replies/2647992