How to set up a "trade/barter" to show up as expense

HTSiordia

I’ve always kept my own books, then used spreadsheet to create invoice. I’ve recently graduated to web-based accounting. I have a client who is also a vendor. I bill them bi-monthly for my time. In the past I’ve included a “Barter/Trade” line item credit (negative amount) on their invoice for any printing they did for me in that respective time frame. How do I enter these transactions in Wave so the “Barter/Trade” shows up in its own account as an “expense” as well as a credit on the invoice?