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. Remember that when you mail a return, you need to include copies of your W-2, etc. with your return.
For your dependent: