He must file an amended return form 1040X and check the box that someone else can claim him. Do not check the box until after the amended return is started. An amended return is form 1040X and it must be printed and mailed. It can't be efiled. In normal times it takes the IRS about 16 weeks to process an amended return. Here is a link for how to amend a return: https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
He will have to print, sign and mail the return. TurboTax does not mail it for him.
You will have to print and mail your return to get it accepted. It takes way too long for the IRS to process his return and clear the fact that he originally claimed himself for your to wait and efile your return.
