You can file a group return using IRS Form 990 for all of your subordinate organizations that fall under a group exemption, provided that your subordinate organizations are
However, a subordinate organization can also choose to file their annual information return separately instead of filing as a group return. In that case, the organization must file an individual Form 990-EZ and must use its own EIN and not that of the central organization or the group return.
If the subordinate organizations decide to file their Form 990 as group return, then it must authorize your organization in writing to include them in the group return and provide a statement of declaration that the information submitted is true and complete.
Once the authorization process is done, you should send the annual information return that maintains the group exemption ruling to:
Department of the Treasury
Internal Revenue Service Center
Ogden, UT 84201-0027