When IT cost sits in one central budget line with no visibility into which department is driving it, every department behaves rationally by requesting more IT resource than they would if they actually saw the price attached — because from their perspective it's free. Chargeback and showback are the two mechanisms for fixing that, and they differ in one important way: chargeback actually bills the department for what they consume, showback simply reports it without moving money.
Showback is the easier and usually the right starting point, particularly in an organisation where finance and department budgets aren't structured to handle an internal billing mechanism cleanly. Simply showing a department their actual cloud spend, their software licence cost, their share of the helpdesk's time, changes behaviour on its own — people who can see the number attached to their choices make different choices than people who can't, even with no financial consequence attached.
Chargeback goes further and actually moves the cost onto department budgets, which produces stronger behavioural change and requires real organisational buy-in to implement fairly. It needs an allocation model that departments trust — usage-based rather than an arbitrary even split — because a chargeback model perceived as unfair produces resentment toward IT rather than the intended cost discipline.
Either approach requires the underlying cost data to actually be attributable per department in the first place, which is often the real blocker — cloud spend tagged by project rather than by owning team, or a single shared software licence pool with no per-department usage tracking. Building that attribution is unglamorous infrastructure work, and it's the actual prerequisite that determines whether chargeback or showback can work at all, regardless of which model an organisation decides to adopt.
