Putting him in the "Ward Assistant Clerk" (membership and finance) or "Ward Assistant Clerk—Finance" positions in Leader and Clerk Resources will give him the appropriate access, however, if he was called and sustained as the "Ward Assistant Clerk—Membership" specifically, you should get approval from the stake. You might also consider having him sustained and/or set apart again for the adjusted calling. The stake approves all clerk callings; and in terms of the sustaining, ward members may appreciate knowing when someone new might have access to tithing records, etc.
Samuel Bradshaw • If you desire to serve God, you are called to the work.