---
title: "Quarterly estimated-tax safe harbor (Form 1040-ES): the required annual payment and per-quarter amount to avoid an underpayment penalty."
method: POST
path: "/v1/tax/estimated"
tags: ["Payroll & tax"]
---

# Quarterly estimated-tax safe harbor (Form 1040-ES): the required annual payment and per-quarter amount to avoid an underpayment penalty.

`POST /v1/tax/estimated`

## Request

- Base URL: `` (relative, and it does not resolve against the document’s source URL)
- URL: `/v1/tax/estimated`
- Auth: none declared

Quarterly estimated-tax safe harbor (Form 1040-ES): the required annual payment and per-quarter amount to avoid an underpayment penalty.

Payment: x402 ($0.10 USDC on eip155:8453). Call unpaid to receive an HTTP 402 with requirements, then retry with the PAYMENT-SIGNATURE header. Method: required = min(90% of this-year tax, 100% of prior-year tax [110% if prior AGI > $150k, or > $75k if MFS]); quarterly = (required - withholding)/4

## Request body

- object
  - `expectedTaxThisYear` number, required
  - `priorYearTax` number, required
  - `priorYearAGI` number, required
  - `withholdingThisYear` number
  - `filingStatus` 'single' | 'mfj' | 'hoh' | 'mfs'

## Response `200`

Verified result + provenance (formula, sources, reproducible SHA-256 hash).

## Other responses

- `400`: Invalid input (no charge) — body echoes the JSON Schema.
- `402`: Payment required — PAYMENT-REQUIRED header carries the x402 accepts[] quote.

---

[API](https://skmtc.dev/x402toll/apis/tollbooth-verified-calculators-for-ai-agents.md) · [All operations](https://skmtc.dev/x402toll/apis/tollbooth-verified-calculators-for-ai-agents/llms.txt) · [OpenAPI document](https://skmtc.dev/x402toll/apis/tollbooth-verified-calculators-for-ai-agents/revisions/60cb70a3e1a5?raw)