invoice arithmetic audit derived

{
  "input": {
    "body": {
      "policy": {
        "rounding": "half_up",
        "tax_inclusive": false,
        "round_per_line": true
      },
      "invoice": {
        "id": "INV-7781",
        "lines": [
          {
            "quantity": "3",
            "tax_rate": "10",
            "line_total": "59.97",
            "tax_amount": "6.00",
            "unit_price": "19.99",
            "description": "Widget"
          },
          {
            "quantity": "7",
            "tax_rate": "10",
            "line_total": "7.03",
            "tax_amount": "0.70",
            "unit_price": "1.005",
            "description": "Washer"
          },
          {
            "discount": "120.00",
            "quantity": "1",
            "tax_rate": "10",
            "line_total": "-20.00",
            "tax_amount": "-1.82",
            "unit_price": "100.00",
            "description": "Service call"
          }
        ],
        "total": "51.88",
        "currency": "AUD",
        "subtotal": "47.00",
        "tax_total": "4.88"
      }
    },
    "type": "http",
    "method": "POST",
    "bodyType": "json"
  },
  "output": {
    "type": "json",
    "example": {
      "lines": [
        {
          "line": 1,
          "discount": "0",
          "quantity": "3",
          "tax_rate": "10",
          "net_exact": "59.97",
          "tax_exact": "5.997",
          "unit_price": "19.99",
          "net_rounded": "59.97",
          "tax_rounded": "6"
        },
        {
          "line": 2,
          "discount": "0",
          "quantity": "7",
          "tax_rate": "10",
          "net_exact": "7.035",
          "tax_exact": "0.704",
          "unit_price": "1.005",
          "net_rounded": "7.04",
          "tax_rounded": "0.7"
        },
        {
          "line": 3,
          "discount": "120",
          "quantity": "1",
          "tax_rate": "10",
          "net_exact": "-20",
          "tax_exact": "-2",
          "unit_price": "100",
          "net_rounded": "-20",
          "tax_rounded": "-2"
        }
      ],
      "limits": {
        "maxEntries": 20000,
        "maxAccounts": 5000,
        "maxFindings": 500,
        "maxLinesPerEntry": 500,
        "maxStatementLines": 20000
      },
      "passed": false,
      "complete": true,
      "currency": "AUD",
      "findings": [
        {
          "code": "LINE_TOTAL_DISAGREES",
          "line": 2,
          "detail": "line 2 declares 7.03 and 7 at 1.005 gives 7.04 under half_up rounding to 2 place(s), out by exactly -0.01."
        },
        {
          "code": "DISCOUNT_EXCEEDS_LINE",
          "line": 3,
          "detail": "line 3 discounts 120 against a line of 100, so the line is negative by exactly 20."
        },
        {
          "code": "LINE_TAX_DISAGREES",
          "line": 3,
          "detail": "line 3 declares tax of -1.82 and 10% on -20 gives -2, out by exactly 0.18."
        }
      ],
      "invoice_id": "INV-7781",
      "line_count": 3,
      "request_id": "example-request",
      "service_id": "invoice_arithmetic_audit",
      "assumptions": [
        "Quantity times unit price is an exact decimal product, which never loses a digit. Rounding happens only where the policy says it happens, and the policy is stated by the caller rather than assumed.",
        "Rounding per line and rounding the whole invoice give different totals. Both are defensible, so the difference between them is computed and published rather than one being treated as correct.",
        "Tax-inclusive and tax-exclusive are different formulas that do not round to the same figure, which is why an invoice built one way and checked the other is always out by a cent. The policy says which ..."
      ],
      "limitations": [
        "Whether the arithmetic on the invoice supplied is self-consistent under the policy supplied. Not tax advice and not accounting advice: whether a rate is the right rate, whether a supply is taxable, an...",
        "arithmetic_sound is true only when every declared figure matched the computed one and every figure fitted the currency."
      ],
      "minor_units": 2,
      "observed_at": "2026-10-02T00:00:00.000Z",
      "not_examined": [],
      "finding_count": 6,
      "rounding_mode": "half_up",
      "tax_inclusive": false,
      "computed_total": "51.71",
      "service_version": "1.0.0",
      "arithmetic_sound": false,
      "findings_by_code": {
        "TOTAL_DISAGREES": 1,
        "LINE_TAX_DISAGREES": 1,
        "SUBTOTAL_DISAGREES": 1,
        "TAX_TOTAL_DISAGREES": 1,
        "LINE_TOTAL_DISAGREES": 1,
        "DISCOUNT_EXCEEDS_LINE": 1
      },
      "rounded_per_line": true,
      "computed_subtotal": "47.01",
      "computed_tax_total": "4.7",
      "subtotal_exact_unrounded": "47.005",
      "rounding_policy_difference": "0"
    }
  }
}