I have to get my 2014 trough 2016 taxes done. will I only get charged once for processing all 3 years worth of taxes?
There is software for each tax year designed to comply with that year's tax laws. Sorry, but you have to pay for each year's software. Only 2016 can be prepared using the online software and only 2016 can be e-filed.
To file a return for a prior tax year
Only a 2016 return can be prepared online and e-filed.
If you need to prepare a return for 2014 or 2015 you can purchase and download desktop software to do it, then print, sign, and mail the return(s)
(if you want to prepare on paper for free: )
You can download the Forms and Instructions from the IRS web site:
Remember to prepare your state return as well—if you live in a state that has a state income tax.
Note: When you mail your 2014 and 2015 returns use separate envelopes so they do not get overlooked/lost by the IRS. When you mail a tax return, it is a good idea to use a mailing service that tracks it so you will know it made it to the IRS--such as UPS or certified mail.