Your dependent filed a return without saying he could be claimed on your return and your return was rejected? AFTER his return has been fully processed and he has received his refund, he has to file an amended return that says he can be claimed as a dependent on someone else’s return. Amended returns (form 1040X) have to be printed and mailed. They cannot be e-filed; it takes the IRS a couple of months to process them. Meanwhile, since your e-filed return has been rejected, you now have to print and mail it in to the IRS. You will not be able to e-file. You do not have to wait for your dependent’s amended return to be processed. Remember that when you mail a return, you need to include copies of your W-2, etc. with your return.
For your dependent:
A 1040X cannot be e-filed. It must be printed and mailed. It will take about 3-4 months for the IRS to process an amended return. It is a good idea to use a mailing service that will track it, like UPS or certified mail, so you will know it was received.
Wait about 3 weeks from mailing and you can check the status of your amended return:
https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1
https://ttlc.intuit.com/questions/1908543-do-i-need-to-amend