Yes. With TurboTax Online (TTO), you do not have to pay until you are ready to file. The problem is you can only do one return per account and do not get to see all the forms until you pay.    In the on-line version of TT,  the  main Form 1040, 1040A or 1040EZ can be seen (before paying) through Tools, View Tax Summary, Preview My 1040 or  go to Print Center and then choose to Preview.

And the Online web version is only good for the current year.   So only for 2016 now.  With the Online version not all versions have the same forms so you may need to use a higher version.  If you buy the Desktop CD/Download program then all versions have all the same forms so you can use a lower less expenses version.  There are several other big differences between Online and Desktop.

If you want to input the 2015 return you will have to buy & install the 2015 downloaded program which can be bought here :  https://turbotax.intuit.com/personal-taxes/past-years-products/

Good news, if you get the 2015 return in and it matches the original, you can transfer in that info to the 2016 program ... so don't start a 2016 program until you finish the 2015. 

You have to pay for download software before you use it, either current year or past years