Hello Sunyoup Park (박선엽) -Welcome to Microsoft Q&A and thanks for reaching out to us.
Here is the document for the API https://video2.skills-academy.com/en-us/rest/api/billing/2019-10-01-preview/invoices/list-by-billing-subscription?tabs=HTTP that will check the invoice for each subscription of customers who are using Azure plan Subscription.
Hope this helps. and please feel free to reach out if you have any further questions.
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