I have customers who purchase generall 2 items and are not invoiced correctly.

[dollynn]

A customer pays for an item, then moves to another item and pays for it.  They are not given the volume discount.  As a result, they are listed as individual purchases and are not given a combined shipping discount.  I have the policies set up, but they never seem to happen.  How can I avoid this?  It is very frustrating.  I would like to look at the invoice before it is sent, so I can correct it.  It is very frustrating.  Why set up the policies if they will not be used.  I have tried talking to an agent, but it is still an issue.  I have tried having ebay call me, but I never get a call.  

[kensgiftshop]

The buyer needs to add the items to their cart, then make one payment.

Since they made two different orders, the discount won't work.

[wooden_flower]

You can manually refund the buyer for the discount and the shipping discount (click send refund in your sold items), then use bulk shipping to make one shipping label for the 2 orders - 

https://gslblui.ebay.com/gslblui/bulk

You can try adding a line to your description that says something like ‘please use the cart if you are buying multiple items’. But lots of buyers don’t read the full description.

[disneyshopper]

The volume discount refers to multiple purchases of the same item in one listing.  As explained to you, in order for the buyer to receive a discount for purchases of two different items, the buyer has to use the ADD TO CART option.