Is your cost model an asset, or one person's spreadsheet?
A cost model that lives in one analyst's head and one undocumented spreadsheet is a risk, not an asset. This question reveals whether your model is documented, versioned, owned, and audited, or whether it would leave the building the day its author does.
“Is your cost model documented, version-controlled, owned, and auditable?”
What is cost model governance and documentation?
It is the set of practices that turn a cost model from a fragile personal artifact into a durable, trustworthy asset. Four layers matter: documentation (the logic and assumptions are written down), version control (changes are tracked and reversible), ownership (a named person or team is accountable), and an audit trail (who changed what, when, and why is recorded). Without them, the model is a black box that only its author understands, cannot be checked, and disappears when they leave. Maturity runs from undocumented, to partly documented, to documented and owned, to fully governed. A model people can trust and inspect is worth far more than a precise one nobody can verify.
An unverifiable model is a liability in disguise.
A cost model drives pricing, customer, and investment decisions. If no one but its author can explain how it works, the organisation is betting real money on a black box. When that person is unavailable, or leaves, the model becomes unmaintainable and the decisions it fed become unrepeatable.
Governance removes that fragility. Documentation lets others understand and challenge the logic; version control makes changes safe and reversible; clear ownership makes someone accountable for keeping it right; an audit trail makes it defensible to auditors, regulators, and the board.
The payoff is trust. A model that can be inspected, questioned, and traced is one that decision-makers rely on with confidence, and that survives staff changes, audits, and scrutiny. A precise model that no one can verify carries hidden risk with every decision it touches.
From black box to governed asset.
As governance matures, an undocumented model gains documentation, then version control and ownership, and finally a full audit trail, turning a personal artifact into a durable, trusted asset.
Is your model governed?
Question 6 assesses whether your cost model is documented, versioned, owned, and auditable. Each level adds a layer of foundation beneath the model.
“The model lives in one person's head and an undocumented file.”
There is no written record of how the model works or why. One analyst built it and only they understand it. If they are unavailable, no one can maintain, explain, or trust it, and every decision it feeds rests on an unverifiable black box.
- The model exists only in one person's understanding
- No written logic, assumptions, or record of changes
- The organisation cannot maintain it without its author
- Decisions rest on a box no one else can open
“Some of the model is written down, but there is no real control.”
Key parts of the logic and assumptions are documented, which helps others follow it. But changes are not tracked, there is no version history, and ownership is informal. The model is more understandable than before, yet still fragile and hard to trust fully.
- Documentation exists but changes are not tracked
- No version history means edits can be lost or conflict
- Ownership is informal and unclear
- The model is understandable but not yet controlled
“The model is documented, versioned, and has a clear owner.”
Logic and assumptions are documented, changes are version-controlled and reversible, and a named person or team owns the model and is accountable for it. It can now be maintained, understood, and safely changed by more than one person. The main gap is a formal audit trail.
- Documentation, versioning, and ownership are all in place
- Changes are tracked and reversible
- More than one person can maintain the model
- The remaining step is a full, formal audit trail
“The model is documented, versioned, owned, and fully auditable.”
Every governance layer is present: documentation, version control, clear ownership, and an audit trail recording who changed what, when, and why. The model can be inspected, challenged, and defended to auditors, regulators, and the board. It is a durable organisational asset, not a personal artifact.
- Governance must be maintained, not just set up once
- The audit trail has to stay complete and current
- Controls should enable use, not smother it
- The model is now trusted, inspectable, and durable
Practical steps, level by level.
Quick Wins
- Write down how the model works: its structure, logic, and key assumptions
- Capture the assumptions that are currently only in the author's head
- Store the documentation with the model so they stay together
- Name, even informally, who is responsible for the model
Structural Improvements
- Put the model under version control so changes are tracked and reversible
- Assign a formal owner accountable for keeping it correct and current
- Establish a routine for making and recording changes
- Ensure at least two people can maintain and explain the model
World-Class Practices
- Add an audit trail: record who changed what, when, and why
- Set a regular review cycle so the model stays current and correct
- Make the model defensible to auditors, regulators, and the board
- Keep controls light enough that the model stays used, not shelved
Where governance is non-negotiable.
Every organisation benefits from a governed model, but documentation and audit are essential where models are scrutinised or lives and licences depend on them.
| Industry | Governance Signal | Key Insight |
|---|---|---|
| Healthcare | Audit and safety | Cost and outcome models face regulatory scrutiny; documentation and audit trails are essential, not optional, to defend every figure. |
| Financial Services | Regulatory | Cost and profitability models must be auditable and traceable; ungoverned spreadsheets are a compliance risk in themselves. |
| Manufacturing | Continuity | Complex product-costing models must outlive the analyst who built them; documentation and ownership protect years of embedded logic. |
Would your model survive its author leaving?
Take the free Profitability Health Check to assess whether your cost model is documented, versioned, owned, and auditable, and where it is still a black box only one person can open.