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
