Whenever a person sets out to deliver on a route, a trip sheet can be created in few seconds. The trip sheet has the list of customers and thier supply items to be delivered (accomodating their alterations and cancellations)
This trip sheet will be visible in the delivery person's mobile app who can mark the delivery and/or returns for each customer. It hardly takes 2 seconds to mark delivery for a customer.
When the day comes to send out invoices to customers, you just need to push a button to generate invoices for all the customers.
It will accomodate the customer's prior payments, deliveries and returns and sends out the invoice over email or sms automatically. Its that simple.