Orb allows you to preview the side-effects of the actions you take by including the `Include-Changed-Resources` on most significant billing mutations. 

We're introducing support for a new header value, `payable_invoices`, which returns only invoices that are immediately payable. Note that these invoices will often include only upfront fixed fees, making it a great fit and more performant option for checkout and preview flows. This new header value is also compatible with pending changes.