Nope...any messing with the current year's Online software will mess up what transfers to the next year....and destroy the file that ends up getting saved permanently at the end of every year when the software changes over to the next year.
BUT...the 2018 Online software " should be " locked now and (maybe) shouldn't let you into it to mess with it anyhow. During this change-over period...that is not always certain as the programmers step thru their change steps...but DO Not be tempted to change anything even if it does let you in..... In the coming weeks, the Online 2019 software should be up, but it may be really buggy and useless to you.
Those who use the Desktop/Download software every year do actually have a What-If worksheet that allows you to transfer the current tax year's data into a next year column, and then lets you change the specific entries you think might change, to see how that would affect the next year's taxes ....but the Online software is far more limited and can't do that.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
