It is true the TN doesn't have any income tax, but every state (including the other states that don't have income taxes) are available in the dropdown except TN. When "TN" is printed in Box 15 on a W2, people should be able to put it in the field on TurboTax. Seems like an unforced error to me.
The fact that TX doesn't have state tax doesn't stop it from being an option. TN had to be added in in order for it to work. Regardless of adding it manually. It doesn't appear.
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