Thanks for your reply,

"suggest running a Transaction List by Customers report and looking for split invoice transactions. From there, check the amount of your bill and compare it to the split invoices found in the report. That will help you find the linked invoice to a bill."

We did that, it does not show linked supplier invoices to the invoice issued to the customer,  when you enter the supplier invoice and select "billable" and select a customer to bill to and subsequently bill it out, I was hoping the original supplier invoice can be linked back to the customer invoice issued since they were linked from the supplier's invoice originally to be billed out, we are having issues reconciling our supplier invoices vs what was invoiced to the customer.