Confirming

Completing a task requires confirmation of the customer. When a task is marked completed by the performer, the customer reviews the task and delivered artefacts and either:

If they think the task is complete, marks it as Done.
Otherwise, the task goes back to In Planning and the customer and performer re-plan.

Completion, in general, proceeds "left-to-right" on a task DAG - as smaller tasks are completed, larger tasks upon which they depend may be as well - but all tasks must be explicitly marked complete and explicitly confirmed.

Next, see renegotiating.