ONLINE vs. DESKTOP
When you use Online TurboTax, you get one return per fee. Each return needs its own account and user ID. If you use the same account and user ID for a second return, you overwrite the first one and lose it forever.
When you use Desktop TurboTax, which you install from a CD or download to your own hard drive, you can prepare and e-file multiple returns for the cost of the software. You can e-file up to 5 Federal returns—more if you mail the additional ones. If you have multiple returns to prepare for family members, Desktop is more cost effective.
Desktop --unless you specifically buy federal Deluxe only from a retailer-- will include the software for one specific state. You can prepare as many returns for that state as the number of federal returns you prepare. E-filing state returns is an extra fee which can be avoided by printing and mailing the states. Additional--other--state software is an additional fee for the software.
The CD or download can prepare an unlimited number of returns, although the user license says you can only use it for personal and family returns. Per IRS regulations, you can only e-file 5 returns, but you can print and mail others if you need to.
If you qualify for free online filing, that's clearly cheaper. If you do not qualify for free online filing, the CD or download version is cheaper overall. You will find the best price at legitimate discounters like Costco, Best Buy or Amazon.
Using the TurboTax desktop CD/Download editions you get 5 free federal tax e-files included in the purchase price. The 5 e-files are limited by IRS rules so any other tax returns over 5 will have to be printed and mailed.
You can create, complete and file as many tax returns as needed with the desktop editions at no charge.
Note that one state program download is also included in the purchase price (except Basic). There is an e-file charge for the state tax return, currently $20 with an increase on March 1 to $25. This state e-file charge can be avoided by printing and mailing the state tax return.
TurboTax desktop CD/Download editions - https://turbotax.intuit.com/personal-taxes/cd-download/
Using the TurboTax online editions you can only complete one tax return. To complete additional tax returns using the online editions you would need to create a new account with a new User ID. Also, the state programs are an additional charge using the online editions.
Go to this TurboTax website for the online editions - https://turbotax.intuit.com/personal-taxes/online/