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Corporate financial ratios (Ambient standard pack)

Ambient Core ships two layers of close metrics:

• Primary (existing defaults) — balance-sheet and net-profit metrics already in the shared catalog: current and quick ratios, percent-scale margins (gross_margin, operating_margin, net_margin, ebitda_margin), parameterized dso / dpo, working capital, cash conversion cycle, growth, and burn. These stay the default paths for FP&A and covenant templates inside the product.
• Standard corporate ratio pack (this document) — additional coverage clients expect in credit and corporate-finance workflows: return on equity and invested capital, expense burdens, full utilization and solvency multiples, strict quick assets, and interest-coverage variants. Templates are tagged corporateRatioPack: true in catalog/shared/metrics.yaml.

Golden tests use the synthetic Harbor Ridge fixture in tests/fixtures/ratios/harbor_ridge_ratio_test_cases.json. The Gold contract shape is contracts/finance-corporate-ratios-v1.yaml (FINANCE_CORPORATE_RATIOS).

Ratio inventory

27 primary ratio slugs: return_on_equity, return_on_assets, return_on_invested_capital, gross_margin (legacy percent scale), operating_profit_margin, net_profit_margin, effective_interest_rate, interest_burden, effective_tax_rate, tax_burden, total_asset_turnover, ppe_turnover, cash_turnover, cash_days, accounts_receivable_turnover, accounts_receivable_days, inventory_turnover, inventory_days, accounts_payable_turnover, accounts_payable_days, total_assets_to_equity, debt_to_equity, debt_to_tangible_net_worth, debt_to_ebitda, current_ratio, quick_ratio, ebitda_to_interest.

Five documented variants: ebitda_margin, net_debt_to_ebitda, ebit_to_interest, ebitda_less_capex_to_interest, fixed_charge_coverage, plus the strict quick ratio quick_ratio_quick_assets.

Derived line items (catalog slugs): gross_profit, ebitda_derived, nopat, net_debt, invested_capital, tangible_net_worth, quick_assets.

Out of scope: market-value ratios (price/earnings and similar), dollar working capital as a ratio, cash conversion cycle as a bundled KPI, and credit-sales-only DSO as the standard definition.

Global conventions

Balance-sheet basis

Default stock inputs use ending balances for the analysis period (balanceBasisDefault: ending on pack metrics). Average balances are supported by supplying pre-averaged inputs upstream; never mix ending equity with average assets inside a DuPont identity.

Units

• Return, profitability, and expense ratios in this pack store decimal quotients (0.12 = 12%). Legacy *_margin templates still use percent points (12 = 12%).
• Turnover, leverage, and coverage metrics use multiples (x).
• Day metrics use days.

Day counts

Implement days = 365 / turnover and days = stock × 365 / flow for annual periods. Do not use turnover / 365. For non-annual periods, scale with the period’s day count (annualize or use actual days in the stub); the catalog default path is annual with 365.

Quick ratio — two definitions

Many print examples mix prose and arithmetic. Ambient exposes both:

1. quick_ratio (default) — (current_assets - inventory) / current_liabilities (formula-box style).
2. quick_ratio_quick_assets (alternate) — (cash + marketable_securities + accounts_receivable) / current_liabilities.

Harbor Ridge ending values: current assets 330,000; inventory 120,000; cash 80,000; marketable securities 20,000; receivables 100,000; current liabilities 140,000.

• Default: (330,000 − 120,000) / 140,000 = 1.5x
• Strict quick assets: (80,000 + 20,000 + 100,000) / 140,000 = 1.4286x

A commonly circulated worked example that lists cash, securities, and receivables but omits securities from the sum is arithmetically inconsistent; our golden test uses the full strict numerator above.

Cash, PP&E, ROIC tax rate

• Net debt and cash turnover/days use the cash line only by default. Treat cash + cash equivalents (and optionally short-term investments) only when mappers set an explicit policy field upstream.
• PP&E turnover uses net PP&E (ppe_net).
• ROIC / NOPAT uses the period effective tax rate (tax_expense / earnings_before_tax when EBT > 0). A statutory rate may be supplied explicitly when EBT ≤ 0.

Undefined and edge cases

The reference evaluator (ambient_calc) returns null for divide-by-zero and missing operands (never infinity). Use safe_eval_result or compute_metric_result when you need structured null_reason codes (zero_denominator, missing_input, null_operand); bare safe_eval remains value-only for backward compatibility.

IFRS / HKFRS vs US GAAP

• IFRS 16 / HKFRS leases: finance lease liabilities with interest accrue into interest_bearing_liabilities; right-of-use amortization affects EBITDA comparability across reporters — document lease policy in lineage.
• Interest classification: gross interest expense is the default for coverage; net finance income may require note disclosure under IFRS.
• ROE and NCI: align net_income and total_shareholders_equity to the same consolidation scope (parent-only vs consolidated including non-controlling interest).

DuPont identities

Tests assert (annual, ending basis, Harbor Ridge fixture):

• ROE = ROA × equity multiplier
• ROA = net profit margin × total asset turnover
• ROE = net profit margin × total asset turnover × equity multiplier
• Net profit margin = tax burden × interest burden × EBIT margin
• Five-lever ROE product matches direct ROE within 1e-10 absolute tolerance
• Tax burden ≈ 1 − effective tax rate when tax articulation holds

Mapping to legacy metrics

• accounts_receivable_days — legacy dso uses credit sales and a caller-supplied days count.
• accounts_payable_days — legacy dpo uses a caller-supplied days count; COGS denominator matches the standard.
• inventory_turnover — industry pack metrics may use average inventory; the core pack uses ending inventory.
• operating_profit_margin — legacy operating_margin stores percent points instead of a decimal quotient.
• net_profit_margin — legacy net_margin stores percent points instead of a decimal quotient.

Files

• This spec: docs/ratios/corporate-ratios.md
• Fixture: tests/fixtures/ratios/harbor_ridge_ratio_test_cases.json
• Tests: tests/test_corporate_ratios.py

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Canonical source: ambient-core at docs/ratios/corporate-ratios.md (sync ref cc3d169).