Source: https://guthlabs.ai/docs/instruments/depreciation-calculator-straight-line/

instrument / verified-clean

# Depreciation Calculator (Straight-Line)

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/depreciation-calculator-straight-line/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/depreciation-calculator-straight-line/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/depreciation-calculator-straight-line/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/depreciation-calculator-straight-line/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Finance, Economics & Business (educational only — never individualized investment, tax, or legal advice)

**Tranche**: tranche-5

**Evidence ID**: t5-130

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The straight-line annual depreciation formula is standard and correct under the stated assumptions. Verdict is NEEDS_REVIEW because the instrument also claims to produce a book value schedule without specifying its formula, boundary behavior, partial-year handling, validation constraints, or rounding policy. The educational-only and non-tax-filing label is appropriate.

### Formula and scope findings

- The annual depreciation formula is correct for straight-line depreciation: (cost - salvage value) / useful life.

- The claimed book value schedule lacks an explicit formula. It should define book value at time t as cost - (annual depreciation × elapsed years), with book value not falling below salvage value and ending at salvage value at the end of useful life.

- The specification does not state whether partial years are supported or how schedules should be rounded.

### Unit assumptions

- Cost and salvage value use the same currency and monetary units.

- Useful life is measured in years, not months; a 48-month life must be converted to 4 years before applying the formula.

- Annual depreciation is assumed to be a constant amount per year.

- The schedule is assumed to report beginning book value at year 0 and ending book value at the useful-life endpoint.

## Boundary hardening

### Recorded hazards

- Useful life of zero causes division by zero and must be rejected.

- Negative or nonnumeric useful life must be rejected.

- Salvage value greater than cost produces negative depreciation and should be rejected or explicitly handled.

- Negative cost or salvage values require validation and should generally be rejected.

- Without a floor at salvage value, rounding or extra elapsed periods can reduce book value below salvage value.

- The currency is unspecified; cost and salvage value must be in the same currency and unit.

- A fractional useful life requires defined treatment for partial-year depreciation and schedule display.

- Rounding policy is unspecified; displayed annual depreciation and book values may not reconcile exactly unless precision is defined.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "cost": 12000,
    "salvage_value": 2000,
    "useful_life_years": 5
  },
  "expected_outputs": {
    "annual_depreciation": 2000,
    "book_value_schedule": [
      {
        "year": 0,
        "book_value": 12000
      },
      {
        "year": 1,
        "book_value": 10000
      },
      {
        "year": 2,
        "book_value": 8000
      },
      {
        "year": 3,
        "book_value": 6000
      },
      {
        "year": 4,
        "book_value": 4000
      },
      {
        "year": 5,
        "book_value": 2000
      }
    ]
  },
  "working": "Depreciable base = 12,000 - 2,000 = 10,000. Annual depreciation = 10,000 / 5 = 2,000. Book values: year 0 = 12,000; year 1 = 12,000 - (1 × 2,000) = 10,000; year 2 = 12,000 - (2 × 2,000) = 8,000; year 3 = 12,000 - (3 × 2,000) = 6,000; year 4 = 12,000 - (4 × 2,000) = 4,000; year 5 = 12,000 - (5 × 2,000) = 2,000."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

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

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche5/tranche5-results.json`