for online a separate account is needed for each taxpayer. A unique ID is required but the same e-mail can be used
if you use one of the desktop apps, it's probably cheaper. One fee covers the federal and one state return but there is usually an additional fee for e-filing state. You can do as many returns as you want with no additional fee. You can save each of them. Turbotax automatically uses the taxpayer's name. You are limited to e-filing 5 returns. That's an IRS limit not a Turbotax limit.
