50/30/20 Budget Splitter implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t4-104

Effect

Computation or source lookup only

Input and validation requirements

The formulas themselves have no division-by-zero or branch regime, but the specification leaves negative-income handling and percentage conventions unstated. A UI that accepts negative income can display nonsensical negative allocations, and chart normalization at zero income can encounter 0 divided by 0. Extreme finite inputs also expose floating-point precision and possible overflow beyond the tested magnitude.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "net_income": 5000,
    "currency": "USD",
    "income_period": "monthly",
    "custom_split_percent": [
      50,
      30,
      20
    ]
  },
  "expected_outputs": {
    "needs": 2500,
    "wants": 1500,
    "savings": 1000,
    "pie_breakdown": {
      "needs_percent": 50,
      "wants_percent": 30,
      "savings_percent": 20
    }
  },
  "working": "needs = 0.50 × 5000.00 = 2500.00; wants = 0.30 × 5000.00 = 1500.00; savings = 0.20 × 5000.00 = 1000.00; check: 2500.00 + 1500.00 + 1000.00 = 5000.00."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json