Diagnosis
Since the account is still in a hierarchy, you cannot close it.

Procedure
To remove the account from the hierarchy and close it, proceed asfollows:
Set the Valid To date of the hierarchy to the last (or next)account balancing date by choosing Hierarchy -> Change Interval.Make a note of the original Valid To date of the hierarchy.
Create a new hierarchy. Use the hierarchy that you changed above as thecopy template.
Valid From: One day after the new Valid To date of thechanged hierarchy.
Valid To: Old Valid To date of the original hierarchy.
In the hierarchy, delete the related account that is to be closed.
Now you can enter the account closure date and close the account.