Key Points
- The original Z-score assigns weights to five ratios covering liquidity, retained earnings, operating profitability, market capitalisation and asset turnover.
- A score below 1.81 falls in the "distress zone" where Altman's 1968 study found a high probability of bankruptcy within two years.
- The model is an indicator, not a conclusion; ISA 570 requires the auditor to evaluate all available evidence before forming a going concern opinion.
- Modified versions exist for private companies (Z'-score) and non-manufacturing or emerging-market entities (Z''-score), each with different coefficients and fewer variables.
What is Altman Z-Score?
Edward Altman published the original Z-score model in 1968, using multiple discriminant analysis on a sample of US manufacturing companies. The formula is Z = 1.2X1 + 1.4X2 + 3.3X3 + 0.6X4 + 1.0X5, where X1 is working capital to total assets, X2 is retained earnings to total assets, X3 is EBIT to total assets, X4 is market value of equity to book value of total liabilities, and X5 is sales to total assets. A score above 2.99 places the entity in the "safe zone." Between 1.81 and 2.99 is the "grey zone." Below 1.81 is the "distress zone."
ISA 570.10 requires the auditor to consider whether events or conditions exist that may cast significant doubt on the entity's ability to continue as a going concern. ISA 570.A3 lists financial indicators (adverse key financial ratios, substantial operating losses, inability to pay creditors) as examples. The Z-score aggregates several of those indicators into one metric, which makes it a useful screening tool during planning. It does not replace the auditor's own assessment. ISA 520.5 requires any analytical procedure to use data reliable for the intended purpose, so the auditor verifies that the input ratios reconcile to audited figures before placing weight on the output score.
Worked example
Client: German engineering company, FY2025, revenue €28M, HGB reporter. The engagement team is evaluating going concern indicators at the planning stage. Hoffmann is a private company, so the team applies the Z'-score (the private-firm variant, which replaces market capitalisation with book value of equity in the X4 variable): Z' = 0.717X1 + 0.847X2 + 3.107X3 + 0.420X4 + 0.998X5.
Step 1 — Gather the input variables from the draft financial statements
Working capital is €2.8M, total assets €22.4M, retained earnings €6.7M, EBIT €1.9M, book value of equity €8.4M, book value of total liabilities €14.0M, and sales €28.0M.
Documentation note: record each input with its trial balance reference. Cross-reference working capital to the current asset and current liability classifications. Confirm EBIT reconciles to the statement of profit or loss.
Step 2 — Compute each ratio
X1 = €2.8M / €22.4M = 0.125. X2 = €6.7M / €22.4M = 0.299. X3 = €1.9M / €22.4M = 0.085. X4 = €8.4M / €14.0M = 0.600. X5 = €28.0M / €22.4M = 1.250.
Documentation note: present the five ratios in a table alongside the prior-year comparatives. Flag any ratio that has moved by more than 20% year-on-year for investigation under ISA 520.5.
Step 3 — Apply the Z'-score coefficients
Z' = (0.717 x 0.125) + (0.847 x 0.299) + (3.107 x 0.085) + (0.420 x 0.600) + (0.998 x 1.250) = 0.090 + 0.253 + 0.264 + 0.252 + 1.248 = 2.107.
Documentation note: record the weighted calculation and the total score. Note that the Z'-score distress threshold for private firms is 1.23 (grey zone: 1.23 to 2.90, safe zone: above 2.90). Hoffmann's score of 2.107 sits in the grey zone.
Step 4 — Interpret and corroborate
A grey-zone score does not by itself trigger a going concern doubt. The team corroborates by reviewing Hoffmann's cash flow forecast, the status of the €5M revolving credit facility (€3.2M undrawn), the order backlog (€9.4M covering approximately four months of revenue), and the absence of covenant breaches. ISA 570.16 requires the auditor to evaluate management's assessment and to consider the same period (at least twelve months from the reporting date).
Documentation note: document the Z'-score as one of several indicators assessed. Record the corroborating evidence (cash flow forecast, facility headroom, order backlog). State the conclusion: the grey-zone score warrants continued monitoring but does not, in combination with the other evidence, give rise to material uncertainty.
Conclusion: Hoffmann's Z'-score of 2.107 is documented as a grey-zone result, corroborated by positive cash flow projections and available credit headroom, producing a defensible going concern assessment with no material uncertainty identified.
Why it matters in practice
Teams sometimes treat the Z-score as determinative rather than indicative. ISA 570.A3 lists adverse financial ratios as one category of indicator, not as a standalone conclusion. A distress-zone score that is not followed up with cash flow analysis, covenant review, and management inquiry fails the requirement in ISA 570.16 to evaluate all available evidence. Equally, a safe-zone score used to skip the going concern assessment altogether ignores the possibility that qualitative factors (loss of a major customer, pending litigation) override a healthy quantitative indicator.
The original Z-score model was calibrated on publicly traded US manufacturing firms. Applying it without modification to a private European services entity produces unreliable outputs because the X4 variable (market capitalisation to total liabilities) has no meaningful equivalent and the X5 variable (asset turnover) behaves differently in asset-light industries. The Z'-score or Z''-score variant should be selected based on the entity's characteristics, and the choice should be documented.
Altman Z-score vs debt-to-equity ratio
| Dimension | Altman Z-score | Debt-to-equity ratio |
|---|---|---|
| What it measures | Multi-factor bankruptcy probability combining five financial ratios | Capital structure leverage from a single ratio (total liabilities to equity) |
| Inputs required | Working capital, retained earnings, EBIT, equity, total liabilities, sales, total assets | Total liabilities and total equity only |
| Predictive vs descriptive | Predictive: calibrated to forecast default probability within a defined time horizon | Descriptive: measures the current leverage position without forecasting future distress |
| ISA context | ISA 570 going concern indicator assessment and ISA 520 planning-stage analytical procedures | ISA 520 analytical procedures and covenant compliance testing |
| Limitation | Calibrated on specific populations; requires variant selection for private or non-manufacturing entities | Captures leverage but ignores profitability, liquidity and asset efficiency |
The debt-to-equity ratio answers one question: how leveraged is the entity right now? The Z-score answers a broader question: given this entity's liquidity, profitability, leverage and efficiency together, how likely is financial distress? Auditors who rely on a single leverage ratio during the going concern evaluation miss the interaction effects that a multi-factor model captures.
Related terms
Frequently asked questions
Can I use the Altman Z-score for a private company?
Not the original version. The original model requires market capitalisation for the X4 variable, which private companies lack. Altman developed the Z'-score variant that substitutes book value of equity for market value, with recalibrated coefficients and a lower distress threshold of 1.23. ISA 520.A4 requires the auditor to evaluate whether the data underlying an analytical procedure is reliable for the purpose, so selecting the correct model variant is part of that evaluation.
Does a distress-zone Z-score mean I must issue a going concern modification?
No. The Z-score is an analytical indicator, not an audit conclusion. ISA 570.17 requires the auditor to conclude whether a material uncertainty exists based on all available evidence, including management's plans to address adverse conditions. A distress-zone score should trigger additional procedures (cash flow forecasting review, lender discussions, order pipeline analysis) rather than an automatic opinion modification.
How often should the Z-score be recalculated during an engagement?
Recalculate at planning (using prior-year audited figures or interim data) and at the completion stage (using year-end audited figures). ISA 570.24 requires the auditor to remain alert throughout the audit to evidence of events or conditions that may cast significant doubt on going concern. If interim figures produced a safe-zone score but year-end figures shift into the grey zone, the auditor documents the movement and the additional procedures performed.