What should I do if I entered wrong information while filing my W-2?

[iang-ero1]

I entered the wrong information for box 12b while filing my w-2. Will that have an effect for federal tax due?

[bosso3]

If you have not filed your tax return(s), go back and make corrections to the W2. 

Federal Taxes > Wages and Income  >  W2   and click the update button to update your W2.

If you have filed your tax returns, you will need to file an amended return.

[LeticiaF1]

As bosso3 mentioned, if you have not filed you can go back and make the change on your W2 Form, to do that you can:

1.  Open or continue your return.
2. From the menu, select Search and type-in W-2.
3. Select the Jump to link in the search results.
4. On the Your W-2 info so far screen, select Edit next to the W-2 you want to change.

If you already filed your return, you might have to file an amended return.  It depends as you mentioned it there is a change to your tax liability.  To file an amended return in TurboTax, you do not have to redo the return, you just have to go back to the return and make the changes you need.  You will also have to wait until the return is fully processed by the IRS. To amend your return:

1. Log in to your TurboTax account
2. Go to Tax Home
3. On the FAQ's on the right side, select How do I amend my return?
4. The option of Amend Using TurboTax will show, select it.

The program will guide you as you make the changes necessary, you do not need to enter anything other than what you are changing.  

See the below TurboTax help articles if you would like more information.  Feel free to reach back if you have additional questions.  

How to File an Amended Tax Return with the IRS

@iang-ero1