Quarterly Estimated Tax Planner mechanism

Model scope

The core min(90% of projected current-year tax, applicable percentage of prior-year total tax) calculation is directionally standard for the regular federal safe-harbor method, but the specification is not complete enough for an unqualified PASS. The product should collect tax year, filing status, prior-year total tax liability, prior-year AGI or a validated high-income flag, withholding, credits, and installment method, and should label the result as a federal educational estimate rather than a guaranteed penalty-avoidance payment.

• The safe-harbor target is generally the lesser of 90% of current-year tax and 100% of prior-year tax, or 110% of prior-year tax for taxpayers subject to the high-income rule; the spec does not define the high-income threshold or collect the taxpayer information needed to apply it.
• The input is described as prior-year tax paid, but the safe-harbor comparison generally uses prior-year total tax liability, not the amount actually paid after withholding and estimated payments.
• Dividing the selected annual safe-harbor target by four assumes the regular equal-installment method. The required installments can differ under the annualized-income installment method, and withholding timing can affect penalty calculations.
• Due dates are year-dependent and can shift for weekends or federal holidays; an undated lookup calendar is insufficient.
• The phrase annual_est_tax is ambiguous: it could mean projected current-year tax, the selected safe-harbor annual payment, or an amount after withholding and refundable credits.

Units and conventions

• All tax inputs and outputs are assumed to be U.S. dollars, with amounts rounded to the nearest cent for actual payments.
• Percentages are decimal fractions: 90%=0.90, 100%=1.00, and 110%=1.10.
• The test vectors interpret prior_year_tax_paid as prior-year total tax liability solely to demonstrate the intended safe-harbor calculation; the product should rename or redefine that input.
• Due dates are interpreted as the 2025 federal individual estimated-tax calendar and do not account for taxpayer-specific state rules or disaster extensions.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "tax_year": 2025,
    "projected_current_year_tax_usd": 10000,
    "prior_year_tax_paid_usd": 9000,
    "high_income_taxpayer": false,
    "installment_method": "regular_equal_installments"
  },
  "expected_outputs": {
    "safe_harbor_annual_payment_usd": 9000,
    "per_quarter_payment_usd": 2250,
    "due_dates": [
      "2025-04-15",
      "2025-06-16",
      "2025-09-15",
      "2026-01-15"
    ]
  },
  "reference_data": {
    "current_year_safe_harbor_percentage": {
      "value": 0.9,
      "source_convention": "IRS Form 1040-ES, 2025; widely tabulated federal estimated-tax safe-harbor rule"
    },
    "prior_year_safe_harbor_multiplier": {
      "value": 1,
      "source_convention": "IRS Form 1040-ES and IRS Publication 505, 2025; widely tabulated standard-income prior-year rule"
    },
    "due_date_rows": [
      {
        "installment": 1,
        "due_date": "2025-04-15",
        "source_convention": "IRS Form 1040-ES, 2025 federal individual estimated-tax calendar"
      },
      {
        "installment": 2,
        "due_date": "2025-06-16",
        "source_convention": "IRS Form 1040-ES, 2025 federal individual estimated-tax calendar"
      },
      {
        "installment": 3,
        "due_date": "2025-09-15",
        "source_convention": "IRS Form 1040-ES, 2025 federal individual estimated-tax calendar"
      },
      {
        "installment": 4,
        "due_date": "2026-01-15",
        "source_convention": "IRS Form 1040-ES, 2025 federal individual estimated-tax calendar"
      }
    ]
  },
  "working": "Current-year safe harbor = 10,000.00 × 0.90 = 9,000.00. Prior-year safe harbor = 9,000.00 × 1.00 = 9,000.00. Selected annual target = min(9,000.00, 9,000.00) = 9,000.00. Quarterly payment = 9,000.00 ÷ 4 = 2,250.00. The four dates are direct lookups from the 2025 IRS calendar."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The specification does not define validation for negative tax inputs or distinguish tax liability from refunds and credits. If a negative prior-year amount is accepted literally, the formula produces a nonsensical negative quarterly payment. Extreme finite inputs do not overflow in this test, but they expose a significant floating-point precision hazard. Year-dated safe-harbor rates and due-date tables also require explicit selection and validation.

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-tranche7/tranche7-results.json
• BOUNDARY_HAZARD_CATALOG.json