You can only file one return per account with Turbotax Online, so you will need to create a second account.

Tip: If you're preparing multiple returns for family members, it's more economical to switch to the TurboTax CD/Download software, which lets you e-file up to 5 federal returns at no additional cost. Here is the link to the Desktop products: https://turbotax.intuit.com/personal-taxes/cd-download/

See this FAQ to create another account: https://ttlc.intuit.com/replies/3288574

If I buy Deluxe download will I be able to share it on different computers for different returns, incl. different OS - Mac and Windows?

You can download the program on different computers as follows:

1. Go to turbotax.intuit.com
2. Look for “Products and Pricing”
3. Click on “Access my Downloads”
4. Sign in and select “Downloads”
5. You will see the products you purchased and have an option to download them

You cannot use the windows version of TurboTax on a Mac computer and vice-versa.