28.4 The role of the supplier in an outcome-based contract
An outcome cannot be achieved by the supplier alone, whereas an output can. This means that the supplier will need to estimate the amount of work they can achieve (e.g. by calculating their expected velocity) and then work with the customer to agree how they commit to this, and how the risk is shared.
Typically, the delivery rate is what goes into the contract, as this is under the control of the supplier. It is possible for the outcome or the benefits delivered to go into the contract instead, or as well, but this will depend on how much risk each party wants to share.