If you do receive a refund, you will have to keep it until you file your amended return. You will have to file a Form 1040X which is the form for amended returns. Your starting point would be the Tax Return which you filed. Then you will make the necessary changes ( since only 1 can itemize, you will make that change along with the other necessary changes).
If you are due a larger refund than on your original return, your amended return should only show the difference and you will receive a separate check for it. If you owe money on your amended return, it will show only the new amount owed, you will have to mail a check with the return.
The option to amend a 2021 tax return will become available later in the tax season.
Please visit How to amend (change or correct) a return you've already filed on further instructions on how to amend the return once that option is available.
