Quarterly Tax Calculator
Free MCP server for US self-employed quarterly estimated taxes. estimateQuarterlyTax computes federal + state income tax, SE tax, and the 4 per-quarter installments from annual net profit, filing status, state, and tax year (2025/2026, QBI-aware); getPaymentCalendar returns the 4 IRS quarterly due dates, rolled past weekends and IRS holidays. Remote endpoint: https://mcp.quarterlytax.al157.xyz/mcp (Streamable HTTP, no auth). Read-only calculations; no data stored.
Hosted MCP Server
npx add-mcp 'https://mcp.quarterlytax.al157.xyz/mcp'Installs into Claude Code, Codex, Cursor and more
Documentation
Your numbers
Business revenue minus expenses — the profit you report.
State tax is a rough estimate — graduated marginal brackets for CA, NY, NJ, HI and OR; single approximate marginal rate elsewhere.
§199A simplified estimate — assumes a non-SSTB business with no W-2 wages paid. Thresholds follow the selected tax year.
tax-rules: 2026 federal states 2025 Rates verified for tax year 2026 — rates change yearly, IRS figures govern. State estimates: 2025 data.
Federal / quarter
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State / quarter
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Safe harbor comparison
Payment calendar
Pay via IRS Direct Pay ↗ Pay via EFTPS ↗
Due dates follow the IRS rule: a date falling on a weekend or legal holiday moves to the next business day. Always confirm on irs.gov before paying.