Cost Allocation Tagging
A mandatory, enforced tagging scheme that attributes every resource to an owner, so spend can be understood and acted on below the level of the whole account.
Without allocation, a cloud bill is one number that nobody owns, and every cost conversation becomes a centralised guessing exercise.
A workable scheme is small and mandatory: owner or team, service or application, environment, and cost centre. Four tags cover most needs. A scheme with twenty optional tags produces inconsistent data and is worse than four enforced ones.
Enforcement is the whole difficulty. Tags applied by convention decay immediately. The mechanisms that work: policy that refuses to create untagged resources, tags applied automatically by the deployment pipeline rather than by hand, and a report of untagged spend that is visibly owned by someone.
Structural allocation complements it: separate accounts or subscriptions per team or environment give allocation for free, at the cost of more accounts to manage — usually a good trade, and it provides blast radius isolation as a side effect.
Shared costs need a stated rule — the platform, networking, observability, shared clusters. Allocate proportionally by usage where it can be measured, split evenly where it cannot, and publish the rule. Unallocated shared cost grows until it dominates the report and nobody can act on any of it.