Australian tax API and MCP server for AI agents

Every calculation on this site is free to use from AI assistants and your own code: connect Claude, ChatGPT, Cursor or any MCP client to our MCP server, call the JSON API, or install the open-source JavaScript library. No sign-up or API key.

Why use it instead of the model's memory? Australian tax rates changed on 1 July 2026 (the 16% rate fell to 15%), and PAYG withholding uses the ATO's own formulas and rounding, not the tax brackets. AI models trained before then get these numbers wrong. These tools use the ATO's published formulas and match every row of the ATO's sample data for 2025–26 and 2026–27.

Connect an AI assistant (MCP)

Server URL (Streamable HTTP, no login):

https://aftertaxau.com/mcp

Claude and ChatGPT: add a custom connector and paste the URL above.

Claude Code:

claude mcp add --transport http au-tax https://aftertaxau.com/mcp

Cursor, Windsurf and other clients (mcp.json):

{
  "mcpServers": {
    "au-tax": {
      "url": "https://aftertaxau.com/mcp"
    }
  }
}

Run it locally instead (Node 18 or later, works offline):

{
  "mcpServers": {
    "au-tax": {
      "command": "npx",
      "args": [
        "-y",
        "au-compliance-kit",
        "mcp"
      ]
    }
  }
}

Tools

Tool	What it does
`take_home_pay`	Take-home pay in Australia for a salary or hourly rate, for 2025-26 or 2026-27.
`salary_for_take_home`	Works backwards from the take-home pay someone wants to the gross annual salary they need in Australia, for 2025-26 or 2026-27.
`payg_withholding`	Exact PAYG tax an Australian employer must withhold from one pay (weekly, fortnightly, monthly or quarterly) under ATO Schedule 1 (NAT 1004), with Schedule 8 for study loans and Schedule 9 for seniors, for 2025-26 or 2026-27.
`bonus_withholding`	PAYG tax to withhold from a bonus, commission or other one-off payment made with a regular Australian pay, using ATO Schedule 5 Method A, for 2025-26 or 2026-27.
`annual_tax_estimate`	Australian income tax for a whole financial year and the likely refund or bill: tax at resident or foreign rates, low income tax offset, seniors and pensioners tax offset, Medicare levy with low-income and family reductions, Medicare levy surcharge and compulsory HELP/study loan repayments, compared with the tax withheld.
`super_guarantee`	Australian superannuation guarantee (12%) an employer must pay on ordinary time earnings, or the split of a total package that includes super into base salary and super (package divided by 1.12).
`identifier_validation`	Checks an Australian Business Number (ABN), Australian Company Number (ACN) or tax file number (TFN) with the official check-digit algorithms, or the format of a BSB or bank account number.
`tax_rates`	Official Australian individual tax rates and thresholds for 2025-26, 2026-27 or 2027-28: resident and foreign resident brackets, low income tax offset, Medicare levy and surcharge thresholds, HELP repayment thresholds, seniors offset and the 12% super guarantee.
`gst_calculation`	Adds 10% Australian GST to a price, or works out the GST included in a GST-inclusive price (the price divided by 11).

JSON API

Every tool is also a plain web address, so an assistant that can only open links can still use it. Send the same fields as query parameters, or POST them as JSON. The OpenAPI description works with custom GPT actions and API clients.

https://aftertaxau.com/api/take_home_pay?salary=80000

{
  "taxYear": "2026-27",
  "perPay": {
    "fortnightly": {
      "grossPay": 3076.92,
      "taxWithheld": 622,
      "takeHomePay": 2454.92,
      "superGuarantee": 369.23
    }
  },
  "year": {
    "grossPay": 80000,
    "taxWithheld": 16172,
    "takeHomePay": 63828,
    "superGuarantee": 9600,
    "basis": "26 fortnightly pays"
  },
  "taxForTheYear": {
    "workDeductions": 1000,
    "standardDeductionUsed": true,
    "taxableIncome": 79000,
    "incomeTax": 14220,
    "lowIncomeTaxOffset": 0,
    "seniorsAndPensionersTaxOffset": 0,
    "workingAustraliansTaxOffset": 0,
    "medicareLevy": 1580,
    "medicareLevySurcharge": 0,
    "studyLoanRepayment": 0,
    "totalTax": 15800,
    "taxWithheld": 16172,
    "estimatedRefund": 372
  },
  "calculatorPage": "https://aftertaxau.com/salary/80000/"
}

curl -X POST https://aftertaxau.com/api/annual_tax_estimate \
  -H "Content-Type: application/json" \
  -d '{"salary": 95000, "deductions": 1800, "studyLoan": true}'

Other tools: /api/take_home_pay, /api/salary_for_take_home, /api/payg_withholding, /api/bonus_withholding, /api/annual_tax_estimate, /api/super_guarantee, /api/identifier_validation, /api/tax_rates, /api/gst_calculation. /api lists them with their fields.

JavaScript library

The same calculations as an npm package with no dependencies, for payroll and HR software. The code is open source on GitHub.

npm install au-compliance-kit

import { calculateWithholding, estimateAnnualTax } from "au-compliance-kit";

calculateWithholding({ earnings: 2026.77, period: "fortnightly", payDate: "2026-11-13" });
// { withholding: 284, scale: 2, ... }

What's covered

PAYG withholding for 2025–26 and 2026–27: tax-free threshold, no TFN, foreign residents, HELP and study loans, Medicare levy exemptions and family variations, tax offsets, seniors and pensioners, and bonuses (Method A).
Income tax for 2025–26, 2026–27 and 2027–28 (an estimate), with offsets, the Medicare levy and surcharge, and study loan repayments.
Super guarantee (12%) and ABN, ACN, TFN, BSB and account number checks.

Not covered yet: working holiday makers, back payments, termination payments, and Fair Work award rates.

Fair use and privacy

The API and MCP server are free for reasonable use. We don't store the amounts you send. Results are general information, not tax advice, and we're not affiliated with the ATO.