16/09 edition: allocate AI costs without inventing precision

Who pays for what was not measured?

An SME uses the same AI service to prepare catalogues and answer support requests. The invoice arrives aggregated. Dividing it by user count would be simple; calling that each team's actual consumption would be something else. Our editorial question is how to close the month without concealing the difference.

We propose a report allowing the finance director to distinguish three portions: attribution supported by records, allocation chosen by management and amounts still unknown. The objective is not a response cost with several decimal places; it is a decision about who funds the service and which measurement is missing.

Three references, three functions

The FinOps Foundation's Allocation capability distinguishes allocation, metadata and shared-cost strategies. Forecasting describes future-spend models as inputs to Budgeting. Budgeting frames approved funding and accountability for it. None of these pages determines the correct percentage for this SME.

The repeated-task case

Hypothetical scenario: a catalogue job is repeated after an error and appears under a different technical identifier. If the team counts only completed jobs, allocation may ignore the consumption that most needs explanation. We do not claim any supplier behaves this way; we choose this case to design a check.

Our proposal retains attempt records alongside the originating job. The report also identifies scheduled work without a user and consumption by the platform service itself. A provisional cost centre needs an owner and a reason; it cannot be a box into which the balance disappears.

Choose a rule that can be challenged

For identifiable consumption, propose direct attribution. For capacity kept available to both teams, present options: central funding, a fixed share or a usage proxy. Choose through an explicit decision with a period and participants, not after discovering who benefits.

If the rule uses requests as a proxy, state the limitation: it does not necessarily measure equivalent workload per request. Show the outcome under a reasonable alternative rule without turning that simulation into a new truth. A difference that changes the funding decision should reach service owners before closing.

Reconciliation before internal charging

This original matrix proposes a verifiable close. Finance approves the convention; engineering explains record coverage. Do not publish a fully allocated balance while an unexplained difference remains. Define rounding tolerance before calculation and show it in the report.

The next month starts with a better question

At close, retain the invoice or cost basis, versioned rule, source records and corrections. If an owner later emerges for an unknown portion, record the adjustment rather than silently rewriting the previous month. Review should explain both the amount and the responsibility change.

For a Portuguese SME, the first improvement may be to stop confusing management allocation with tax accounting. This article does not prescribe accounting or tax treatment. We propose governing service spending: improve measurement only when its decision value justifies the work, while retaining the total and uncertainty. We report no achieved savings or accuracy.