Why are there differences between Azure Cost History monthly totals and Partner Customer Statements?

Products

• CloudHealth

Issue/Introduction

Sometimes the cost history report and the invoice don’t exactly match since we collect the data from 2 separate APIs (one is billing API, one is invoice API).  In other words, Statements might reflect a different billing period (not starting at the beginning of the month or ending at the end of a month), but in the "Billing period" category it is assigned to a specific month: