Mexican Payroll & Tax Calculator

Deterministic Mexican payroll & tax math: finiquito, ISR, aguinaldo, IMSS (2026 tables).

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What it can do

    What data it sees

    Do you need an account

    No: the server works without sign-in

    Deterministic Mexican payroll & tax math: finiquito, ISR, aguinaldo, IMSS (2026 tables).

    How to connect

    How to connect Mexican Payroll & Tax Calculator to Claude

    The server address to paste into Claude settings:

    https://fiscal.tinyapis.dev/mcp

    1. Open Claude (claude.ai or the desktop app).
    2. Go to Settings → Connectors.
    3. Click Add custom connector.
    4. Paste the server address copied below into Remote MCP server URL and click Add.
    5. In a chat, click + → Connectors and switch the new connector on.

    Custom connectors are available on Free, Pro, Max, Team and Enterprise plans (Free is limited to one). On Team and Enterprise an organization Owner adds the connector first under Organization settings → Connectors.

    Authorization

    After you click Add, a sign-in window for the service opens. Sign in with your own account and approve access. Claude never sees your password.

    How to connect Mexican Payroll & Tax Calculator to ChatGPT

    The server address to paste into ChatGPT settings:

    https://fiscal.tinyapis.dev/mcp

    1. Open ChatGPT in a browser (chatgpt.com). A Plus, Pro, Business, Enterprise or Edu plan is required.
    2. Turn on developer mode once: Settings → Apps → Advanced settings → Developer mode.
    3. Open Settings → Connectors and click Create.
    4. Fill in the form: Name (anything), Description (one line about what the service does), MCP server URL (copy it below).
    5. Under Authentication choose OAuth if the service requires sign-in, otherwise None. Click Create.
    6. In a new chat open + → Apps/Connectors and enable the connector.

    OpenAI has renamed this section before (Connectors → Apps/Plugins). If the label differs, search settings for "developer mode". On Business/Enterprise workspaces an admin must allow custom connectors first.

    Authorization

    On first use ChatGPT opens the service's sign-in window. Sign in and approve access.

    How to connect Mexican Payroll & Tax Calculator to Cursor

    The server address to paste into Cursor settings:

    https://fiscal.tinyapis.dev/mcp

    Fastest: click Open in Cursor below and confirm the prompt.

    Manually:

    1. In Cursor open Settings → Cursor Settings → MCP and click Add new global MCP server.
    2. Paste the JSON copied below into ~/.cursor/mcp.json (per project: .cursor/mcp.json in the repo root).
    3. Save the file. The server appears in the MCP list; authorize it there if asked.

    Authorization

    If the service needs sign-in, an authorize button appears next to the server in the MCP list.

    Server tool list (4)

    Raw names from tools/list. Only developers need these.

    calc_finiquitoCompute a Mexican finiquito/liquidación (severance) for a resignation or an unjustified dismissal: prorated christmas bonus, vacations, vacation premium, pending salary, and (for dismissal) 90-day + 20-day/year severance and the seniority premium, with Art. 93 exemptions and separation ISR. Do NOT compute this from memory — LFT bands, UMA exemptions, and the SDI integration factor are table-driven. Returns per-concept gross/exempt/taxable, totals, ISR, deductions, and net_total.
    calc_isrCompute Mexican ISR (income tax) withholding for a monthly or annual income using the official SAT tables and employment subsidy. Do NOT estimate ISR from memory — brackets and subsidy change yearly and must come from this deterministic tool. Returns tax, subsidy_applied, withholding, the period, and the tax-table year used.
    calc_aguinaldoCompute a Mexican aguinaldo (year-end bonus): gross, the UMA-based exempt portion, the taxable portion, its ISR, and the net. Minimum 15 days by law. Do NOT compute from memory — the exemption is UMA-indexed per year. Returns gross, taxable, exempt, isr, net, and the days used.
    calc_imssCompute Mexican IMSS social-security contributions: the SDI (integrated daily wage by seniority) and SBC, plus employer/worker quotas for the five insurance branches. The work-risk premium (rt_premium) is an input. Provide either seniority_years (to derive the SDI) or an explicit sdi. Do NOT compute from memory — quota tables and UMA caps are table-driven. Returns sdi, sbc, employer_total, worker_total, grand_total, and a per-branch breakdown.