Quarterly estimated tax (safe harbor) API

Compute required quarterly estimated payments via the IRS safe-harbor rule — lesser of 90% of this year's tax or 100% (110% if AGI > $150k) of last year's — less withholding, split over four quarters, returning each safe-harbor figure, the required annual payment, and the per-quarter amount. Estimate only. Answers 'how much estimated tax per quarter','safe harbor amount','110% prior-year rule','quarterly payment after withholding'.

Price$0.01per request

MethodPOST

Route/v1/calc/tax-estimated-quarterly

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

taxestimated-taxquarterlysafe-harborwithholding1040-esuscalc

API URLhttps://x402.hexl.dev/v1/calc/tax-estimated-quarterly

Integration docs

Example request

{
  "expectedTax": 40000,
  "priorYearTax": 30000,
  "withholding": 10000,
  "agiOver150k": true
}

Example response

{
  "expectedTax": 40000,
  "withholding": 10000,
  "safeHarborCurrentYear": 36000,
  "safeHarborPriorYear": 33000,
  "priorYearMultiplier": 1.1,
  "requiredAnnualPayment": 33000,
  "totalEstimatedPayments": 23000,
  "perQuarterPayment": 5750,
  "note": "Estimate. Safe harbor = lesser of 90% of this year's tax or 100% (110% if AGI > $150k) of last year's; less withholding, split over 4 quarters."
}

Input schema

{
  "type": "object",
  "required": [
    "expectedTax"
  ],
  "properties": {
    "expectedTax": {
      "type": "number",
      "description": "Expected current-year total tax in USD",
      "examples": [
        40000
      ]
    },
    "priorYearTax": {
      "type": "number",
      "description": "Prior-year total tax in USD",
      "examples": [
        30000
      ]
    },
    "withholding": {
      "type": "number",
      "description": "Expected withholding in USD",
      "examples": [
        10000
      ]
    },
    "agiOver150k": {
      "type": "boolean",
      "description": "True if prior-year AGI > $150k (uses 110%)",
      "examples": [
        true
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}