We have the same challenge. And it impacts both the cost center operational world as well as projects. This is not a solution just a brainstorming in the hope we can find alternative solutions.
What we do now is just expose both data elements in Apptio: We provide drilldown reports for managers to be able to see the Invoice and PO numbers generating actuals, and in the next tab we publish a table with PO, Invoice, resource name, hours and $s. Regardles of the timing of invoice payment.
The current manual process of matching invoice and PO numbers (actuals vs timecards) then looking for names and finally hours is the big stumbling block. Adding the PO and invoice numbers is already challenging due to inconsistent formating in the applications involved, but relatively easy to fix. Matching individual names is a nightmare. In our case just not possible (for now).
I will have our TBMA look to the proposal form Ivan above.