If you’re a CSP partner then it’s important to sell the correct Reserved Instance to a customer, and then to check that the discount is being applied to a virtual machine. This article gives useful instructions for both of these tasks: http://bit.ly/2N5udyZ.
Third-party services purchased through the Azure Marketplace are typically invoiced separately in an Enterprise Agreement, outside of Monetary Commitment. From 1 March, 2018 there were some Linux Support options and Linux virtual machines that were changed to consume Monetary Commitment.
Find the announcement and list of relevant services here: http://bit.ly/2Nn74Ed.