You can amend e-filed returns if they've been accepted and paper-filed returns may be amended after they've been mailed. In both situations, wait until after you have received your refund to amend.
Select from the following tax years for specific amending instructions:
Once you begin the amendment process you will see your original return. Please make changes to only those areas of your return that need amending. The refund calculator will start new at $0 and only reflect the changes in the refund (or tax due based on the amendment.)
Keep in mind: You have 3 years from the date you filed your return or 2 years after you paid the tax due (whichever is later) to file an amendment.