Use fixed price for a stable result
Fixed pricing works when deliverables, responsibilities, feedback, and acceptance are clear. It gives the client budget certainty and rewards efficient delivery.
The provider carries estimation risk, so the scope and change process must be strong enough to protect the fee.
Use hourly or day rates for variable work
Time-based pricing fits advisory access, evolving backlogs, client-directed support, and work whose volume cannot be known in advance.
Set a reporting rhythm, approved cap, minimum booking unit, and notice point before the budget is consumed.
Use a hybrid when uncertainty is uneven
Price discovery by time, then quote a fixed implementation after requirements are known. Or use a fixed core scope with an hourly rate for approved additions.
Explain which model applies to each phase so invoices and responsibilities remain predictable.