Currently, it's not possible to merge two already existing accounts together. Movement of any existing amounts on existing accounts must be booked manually through a journal entry.

    If though, an account needs to be renumbered to an account that does not already exist in the system, this is possible, as long as the accounts are in the same category.

    If an account (and its activity) need to be renumbered/moved to a different account number that does not already exist within the same account category (asset, liability, etc.), re-number the account.  The activity remains with the re-numbered account.

    If the new account is not the same account category or both of the accounts already exist:
    1. If the account has already been marked as inactive, mark it as Active temporarily
    2. Create the new account if needed  
    3. Make a manual journal entry to transfer the balance of the old account to the new account
    4. Mark the old account as Inactive - prevent data entry and posting