I may need to file an extension, how do I do this? My grand daughter I claimed she lives with me her mother tried to claim also. We need to know how do we fix remove her?

[Texas Roger]

You don't need an extension if you have already filed and it has been accepted. You just need to prepare an amended tax return form 1040X to remove her as a dependent. If her mother's return was rejected, her mother will have to print and mail her return to get it accepted. This is all assuming that the mother is going to claim your grand daughter on her tax return and you want to take her off your tax return. 

Here are instructions for amending a tax return: https://ttlc.intuit.com/questions/4667233-how-do-i-amend-a-2018-return-in-turbotax