I’m currently working on a purchase flow for a service-based product. In other words, there’s no shipping involved. In doing some research and reviews on an acceptable way to set expectations for how taxes are calculated, I stumbled across a great resource produced by Baymard Institute. They’ve created several usability reports, one of which is dedicated to the Checkout Usability in which Baymard has evaluated 100 retail websites on a set of usability guidelines. Ultimately each site is scored across 6 individual components: Flow, Focus, Data Input, Copywriting, Layout, and Navigation, and then ranked from 1-100. While you need to purchase the report in order to see the positive and negative critiques, the site does allow you to view the benchmark results, as well as filter the sites in several categories. It’s awesome if you need to view multiple examples of shopping carts and checkout flows quickly and without having to go through the flows on 100 retail sites.