@Dnyaneshwar Surywanshi Thank you for your post and I apologize for the delayed response!
You can use the invoices API or SDK to get invoices for modern CSP.
https://learn.microsoft.com/en-us/rest/api/billing/2020-05-01/invoices/list-by-billing-account
If you want to get the line-items for an invoice, you can use Transactions API/SDK
https://learn.microsoft.com/en-us/rest/api/billing/2020-05-01/transactions/list-by-invoice
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