United States
The United States has the deepest catalog here. The IRS's Direct File release exposed a real federal filing implementation, but the repository is now archived, may contain unpatched vulnerabilities, and should not be used in production. Around that historical reference are community filing engines, Form 1040 libraries, crypto cost-basis tools, policy models, and MCP servers.
Maintained filing implementations and state coverage. Federal reference material is unusually rich, but most state systems have no open implementation.
18 projects tagged United States, ranked by community stars.
Privacy-focused, free, open-source cryptocurrency tax calculator for multiple countries: it handles multiple coins/exchanges and computes long/short-term capital gains, cost bases, in/out lot relationships/fractioning, and account balances. It supports FIFO, LIFO, HIFO and it outputs in form 8949 format. It has a programmable plugin architecture
USA Federal Individual Income and Payroll Tax Microsimulation Model
The PolicyEngine US Python package contains a rules engine of the US tax-benefit system, and microdata generation for microsimulation analysis.
The deterministic tax engine for AI agents. Highest score ever recorded on TaxCalcBench (96% exact returns)
Python library to compute US federal taxes, and state taxes for some states.
An overlapping generations model framework for evaluating fiscal policies.
Fully open-source US federal tax engine. Single binary cli. Runs on macOS, Linux, and Windows. Built for AI agents using AI agents.
TAXSIM emulator using the PolicyEngine US federal and state tax calculator
Runloop's AI TaxMan Project: an agent development starter that uses Codex & W&B Weave to process tax forms. Watch YouTube series: https://youtu.be/an7OMH_i8DU
TaxEase.AI is a user-friendly AI assistant designed to demystify and simplify US tax filing, a system that has become needlessly convoluted and stressful for millions of Americans.
MCP server for US individual taxpayers — 39 tools for federal/state tax calculations, credits, deductions, retirement strategies, and tax planning. All calculations run locally. TY2024 + TY2025 (OBBB Act).
MCP server for AI-assisted tax filing through FreeTaxUSA using Playwright browser automation
Free equity-compensation tax optimizer for AI agents — ISO/AMT, NSO, RSU sell-vs-hold, QSBS, concentration & hedging. Deterministic math, federal + 50 states + DC, multi-year plans. Remote MCP + REST, no signup.
MCP server for AgentTax — tax compliance tools for AI agents