Deleting an account that has transfer transactions

Something to consider:  If you delete that account you will lose all historical data for it which can be problematic if you do budgeting or use Tax Planner.  If instead of deleting the account you simply close it you will keep all that historical data and your linked transactions with it will remain intact.  And once the account is closed you can hide it so it does not show up in the Account List and Category List.