Fixed Time & Fixed Price

Fixed Time & Fixed Price engagement model represents the highest level of commitment that OSB will be taking. It applies in contexts where not only technology and requirements are clearly defined upfront and are not likely to change, but also where strict deadlines must absolutely be met - for instance in case of technology retirement, or introduction of legal requirements.

This is the black-belt of OSB engagement models - very rarely applied though.

Dimension	Description / Impact
Control of the activities	In this mode, OSB is fully managing the resources and activities, including tasks allocation and priorities. An OSB Project Manager (a.k.a. Customer Success Manager or CSM) is allocated to the project.
Pricing Model	Based on the detailed effort estimates, resources costs and other financial aspects (such as software licenses, travel expenses, effort contingency, potential warranty, etc...) the project price is calculated and negotiated with the client. Once they have been approved, the project budget and execution timeline are fixed and OSB will only be paid the contracted amount, regardless of the actual effort spent and number of resources involved - unless change requests are negotiated and approved.
Budget Management	Prior to the start of the engagement, the customer requirements are analyzed, the required team composition defined, a detailed tasks breakdown and project plan established, and the effort per resource / profile carefully estimated. The budget is then calculated (see above) and validated with the client. Along project execution, actual efforts spendings + remaining estimated efforts are monitored to measure project health and profitability.
Scope Management	Since the budget is fixed, it is critical to ensure that any deviation (functional, technical or other) from the initial scope is immediately raised. The impact in terms of efforts and costs has to be estimated and submitted to the client, who will either accept the change request (with additional budget approved for execution), or decline it. Only approved Change Requests will be added to the scope to be delivered.
Timeframe	The project planning is established and negotiated with the client at the beginning of the project, accounting for deadlines to be met and resources allocation (on both sides). The progress vs planning must be carefully monitored, as given the contractual commitment to deliver by fixed milestones OSB may have to inject additional resources to meet the deadlines (at its own costs...).
Reporting	A regular project status report of team achievements, scope delivered (incl. change requests submitted), status vs milestones & deadlines, decisions taken and project risks register is provided to the client. There are NO timesheets submitted to the client.
Invoicing	The payment milestones are negotiated at the beginning of the project, and are typically linked to key project milestones/dates (e.g. end of design, end of development, delivery for UAT, go to PROD, end of Hypercare...). They are formally triggered by the PM/CSM when the milestone is reached and validated by the client.