Discount on invoice

Hi, How do I give a buyer a discount on multiple purchases on a combined invoice. Everytime I try to do it, it says invalid. Thanks.

eBay only lets you discount up to the value of the postage. If you have free postage you can't discount any amount at all.

If you can't discount because of Free Post but want to thank the buyer for multiple purchases you can either include a bonus item or send the buyer a partial refund through PayPal.