I forgot to add a state to my federal return. My federal return has been accepted. So how can I file my state return

To add another state to your return in TurboTax Online:

Since your return has been accepted you can now go into your TurboTax return and do an amendment to add the additional state.  

Which option in the amendment should I choose. It seems it always requires me to amend one filed return.

Please be aware that if you are simply ADDING a state return and NOT changing your Federal return, you DO NOT AMEND, you only "Add a State".

 

The instructions for "ADDING" a state return is listed above. 

 

 

 Sign in to TurboTax.

1. Under Your tax returns & documents, select Show, and then select 2018.
2. Now select Add a state (this reopens your return).
3. Select State from the menu on the left (on mobile devices, tap in the upper-left corner to open the menu).
4. On the Let's get your state taxes done right screen, select Continue and follow the onscreen instructions.

If you need to AMEND a return, please start a new question. This question is asking how to add a state return. 

For example, this screenshot of my 2021 tax return. It doesn't have "Add a State" button. Does "Add a State" only work for current year? How do I add a state for previous tax return.

Yes, Add State is only good for the current year. In your case, you will need to:

 

 

1. Select Amend (change) return, then  Amend a filed return.
2. Follow the on screen directions to start an amendment, but don't make any changes in your federal return.
3. Once you are in the return, select the State tab and add the state that you need. 
4. When you are done with that state, click on the Forms icon in the upper right corner. 
5. Find Form 1040-X on the list on the left.
6. Highlight it, then click Delete in the lower left corner of the reading pane.
7. Click on Step by Step in the upper right corner to return to the interview.

 

 

I noticed that you already have several state returns. If you get Error 190, that means you haven't installed all of the states included in your .tax file. 

 

You may need a little more help with your amendment. Click here to get additional help.