Do you manage people by job, or by position? It sounds like terminology. It is the second-biggest structural decision in the whole implementation — behind the legislative data groups and ahead of everything that follows.
Job-based: a job is a role definition — "Financial Analyst" — and any number of people hold it. The assignment carries the job plus a department, a grade and a location, each set individually. Position-based: a position is a specific seat — "Financial Analyst, Treasury, London, reporting to the Treasury Manager" — and the part that does the work is that it exists whether or not anybody is in it, with the assignment inheriting its attributes rather than restating them.
What positions give you: headcount control, because an empty position is a visible, budgetable vacancy; consistency, because attributes are inherited rather than typed and so cannot be typed wrong; position-based approvals and hierarchies; and integration with budgeting and recruiting on a seat basis.
What positions cost you, given the same weight deliberately: a position must exist before anybody can be hired into it, so HR maintains a catalogue that grows forever; every organisational change becomes a position change rather than an assignment change; and volume — a five-thousand-person organisation may need five thousand positions, plus vacancies, plus the historical ones you keep.
Who uses which, as observed tendency rather than law, because it gets quoted as law: public sector, healthcare, education and unionised or headcount-controlled environments tend toward positions; commercial organisations with fluid structures tend toward jobs. That tells you where to start the conversation, not the answer for the client in front of you.
Five questions that do tell you. Is headcount budgeted and controlled at the seat level? Do vacancies need to exist as objects before recruiting? Is there a works council or an agreement defining establishment posts? Does the client have the HR operations capacity to maintain a position catalogue? Is the structure stable, or does it change monthly? Question four is the one nobody asks, and it produces the most expensive failure in this module.
And the switching cost, which is what makes this a design decision rather than a preference. Jobs to positions after go-live means creating a position for every existing assignment and re-pointing every one of them. Positions to jobs means losing the control the client presumably wanted. Neither is a change request — say that while the decision is still open.
The hybrid is legitimate and nobody teaches it: positions for part of the organisation and jobs for the rest. It is also more complex — two operating models and two answers to every question about how something works. It is worth it when part of the organisation genuinely has seat-level control and the rest genuinely does not. It is not worth it as a compromise between two people in a workshop who could not agree.