First if you have a refund the extension was not even needed.
Next if you owe you should have attached a copy of the rejection notice to the mailed in return ... if you did not then make sure to keep a copy incase the IRS questions it.
Lastly ... the child must amend their return to "unclaim" themselves then they are forbidden to file before you do in the future or before you can review the return to make sure they don't make the same error as long as they are your qualifying dependent.
