That is an interesting issue. If the TurboTax software doesn't indicate there are any errors on your return (after you go through the error-check step at the end of your tax return input process), then we would have to say that "NA" (a.k.a. Not Applicable) should be acceptable to use as part of an address.
Everybody, including the IRS and your state department of revenue, knows what NA means, and will therefore ignore the value if they ever attempt to use the address to mail you a notice, an income tax refund, or for any other correspondence.
Because taxpayer addresses are usually entered on the federal side of the program, and then flow-through to the state module from there, we would respectfully recommend jumping back to the beginning of the taxpayer information section (please see the attached screen-capture images for a visual aid) and trying to see if you can change anything relevant to your apartment number there. It might flow-through to your state form.
Another alternative, if the software doesn't like NA as a value, might be to simply enter Apt. 0 or Apt. 1 (indicating that there is no other such dwelling unit at your particular street address).
Finally, if you have further
questions, encounter any difficulties, or just want to speak with a live tax
expert who can walk you through your TurboTax entries (including the ability to
screen-share with your computer), please feel free to contact us. We
would be happy to help you (and as a paying customer, the call is free to you).
Here is a link where you can create a support ticket and reach us:
https://support.turbotax.intuit.com/contact/
Thank you for asking this question.
