Differences Between Supplier Invoices and Cash Purchases

Supplier Invoice	Cash Expense
A supplier invoice has to have a supplier	A cash expense can be made without specifying a supplier.
A supplier invoice is always on credit	A cash expense is paid for when you enter the cash purchase. This means that the payment transaction is captured at the same time as the expense transaction.
A supplier invoice is always tracked on a supplier	A cash expense cannot be tracked when you do not select a supplier. You can only see the cash expense on the expense account.

Differences between using a supplier and not using a supplier

Using a supplier	Not using a supplier
You can track the purchase on the supplier's account statement.	You can only see the purchase on the expense account.
Supplier statistics are updated.	No statistics on a cash purchase without a supplier.