What forms are you missing when using the TurboTax software?
If you have additional forms to include with your tax return that are not included in the TurboTax program and the forms require that they are to be attached to your federal tax return, Form 1040, you cannot e-file the tax return. It must be printed and mailed with the attached forms.
See this TurboTax support FAQ for printing a tax return for mailing - https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...
