Good morning Gopinath,
We had the same thing happening. To combat the issue, we now issue annual POs for subscriptions and break down the fees in the PO line items. So, nothing is paid without a PO associated with it. Its a change in internal policy and procedure, and you have to get the vendors to reference the PO on their invoices. But, it was an added layer of validation for the company on subscription costs. And, you can create PO burn-down reports out of Apptio, which are helpful for budgeting.
Blessings,
Keith