Shared savings?

I'm working on a few investment opportunities that have come up for this fund. The fund is, obviously, interested in the mechanism for shared savings and while we are starting with a bias on how the funds would flow it's been useful to work through some other scenarios.

We're exploring five shared savings models:

1. Identified Savings
2. Front End Rebates
3. Back End Rebates
4. Transaction Payments
5. Periodic Payments

Identified Savings
This is commonly used by strategic sourcing consultancies that have contingent savings contracts with their clients. Savings are "identified" but not realized prior to payment. Often the milestone for payment is at the time of awarding a contract to a supplier that provides lower costs for a good or service.

Front-end Rebate
In this model the supplier takes on the future purchased volume risk in a contract and pays the client their savings at time of contract award.

Back-end or Volume Rebate
In this model the supplier pays the rebate at some pre-determined point in time, such as quarterly, annually, or at contract expiration. This is normally defined either as a lump-sum payment (thereby having the supplier hold the purchased volume risk) or as a volume related payment (thereby having the client hold the purchased volume risk.

Periodic Payments
Savings are tracked and paid on a periodic basis (often monthly or quarterly). While there can be multiple mechanisms this form of shared savings are managed they are usually based on tracking the volume of purchases over the defined period and applying a savings formula to that volume.

Transaction Payments
Savings are tracked and included in the transaction. Payments are made coincidental with supplier payments for each relevant transaction.