---
title: "Standalone 2026 state income tax for any of 51 US jurisdictions — progressive/flat/no-tax schedules, MFJ doubling — applied to the income you provide."
method: POST
path: "/v1/tax/state-income"
tags: ["Payroll & tax"]
---

# Standalone 2026 state income tax for any of 51 US jurisdictions — progressive/flat/no-tax schedules, MFJ doubling — applied to the income you provide.

`POST /v1/tax/state-income`

## Request

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

Standalone 2026 state income tax for any of 51 US jurisdictions — progressive/flat/no-tax schedules, MFJ doubling — applied to the income you provide.

Payment: x402 ($0.05 USDC on eip155:8453). Call unpaid to receive an HTTP 402 with requirements, then retry with the PAYMENT-SIGNATURE header. Method: tax = marginal state 2026 brackets (MFJ doubles single thresholds); no-tax states return $0

## Request body

- object
  - `state` string, required: 2-letter US state/DC code
  - `income` number, required
  - `filingStatus` 'single' | 'mfj'

## 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)