To set that, using administrator role, go to :
1) Setup>User/Roles>Manage Roles
2) Select the custom accountant role>Edit
4) Add : Financial History
5) Set the *access level of permission accordingly
Using the modified custom role, when you navigate to a transaction/record, the related records tab will be available.
*Access Levels for PermissionsThe following are general definitions of possible access levels for permissions.
VIEW - User has access to view existing files only. The user cannot create new, edit existing, or delete existing files.
CREATE - User can create new and view existing files. The user cannot edit or delete existing files.
EDIT - User has access to create new, view existing, and edit existing files. The user cannot delete existing files.
FULL - User has access to create new files and view, edit, and delete existing files.