Pick the version fitted to the kind of company you're looking at. The cut-offs differ too.
Cumulative profit kept in the business. Negative for a company that has never made money — which is exactly what the model is looking for.
Share price × shares outstanding. Used only by the original public-company model.
Total assets minus total liabilities. Used by the Z′ and Z″ variants.
Altman Z-Score Calculator — full version, with the formula and worked steps ↗