Addon orders, linked to the main order, make it quick and easy to add additional products after the main sales order has been completed. The customer pays for addon order products.
Remedial orders, linked to the main order, are for adding products that maybe damaged or missing. There is no charge to the customer for remedial orders.
The benefit of addons and remedials being linked to a sales order is that the extra cost impact can be factored into the job's margin.
This video shows creating a remedial order, viewing job costings and reporting.