Fully open-source federal tax software. Single binary. Runs on macOS, Linux, and Windows.
Built and maintained by AI agents using official IRS publications as the sole source of truth.
Covers Form 1040 (TY2025) today. Additional forms and state returns coming.
- Professional tax software is closed source and expensive to maintain. Every rule change required manual updates to the codebase
- AI agents have drastically reduced the cost of building and maintaining tax software. It only makes sense to do it in the open
- This project aims to be the first truly open-source, up-to-date tax software that works for everyone
Designed for the AI era:
- Built to be run by AI agents more than humans
- Single binary CLI that AI agents can download and run instantly
- Everything stored locally. Open, secure, and accessible
Inspired by Andrej Karpathy's autoresearch, an autonomous loop where AI agents modify code, measure results, and keep only improvements. OpenTax applies the same idea to tax software: agents read IRS instructions, write implementations, generate test cases, and fix regressions in a continuous loop.
Copy-paste this into Claude Desktop app:
Load the skill here using curl or equivalent:
https://raw.githubusercontent.com/filedcom/opentax/main/skills/opentax/SKILL.md
Then run the onboarding flow.
If you use Claude Code, install OpenTax as a plugin so the skill is always available:
- Add the marketplace:
/plugin marketplace add filedcom/opentax
- Install the plugin:
/plugin install opentax@opentax
- Use the skills:
/opentax:opentax # guided onboarding, picks the right skill for you
/opentax:tax-preparer # prepare a return from scratch
/opentax:tax-reviewer # audit a completed return against source docs
One command. No runtime, no installer, no dependencies.
curl -fsSL https://raw.githubusercontent.com/filedcom/opentax/main/install.sh | sh- Detects your OS and architecture automatically
- Downloads the right binary and puts it in your PATH
Or download manually:
| Platform | Download |
|---|---|
| Mac (Apple Silicon) | opentax-macos-arm64 |
| Mac (Intel) | opentax-macos-x64 |
| Windows | opentax-windows-x64.exe |
| Linux (x64) | opentax-linux-x64 |
| Linux (ARM) | opentax-linux-arm64 |
$ opentax return create --year 2025
{ "returnId": "a1b2c3" }
$ opentax form add --returnId a1b2c3 --node_type general '{"filing_status": "single"}'
{ "id": "general_01", "nodeType": "general" }
$ opentax form add --returnId a1b2c3 --node_type w2 '{"box1_wages": 55000, "box2_fed_withheld": 5200}'
{ "id": "w2_01", "nodeType": "w2" }
$ opentax return get --returnId a1b2c3{
"returnId": "a1b2c3",
"year": 2025,
"summary": {
"line1z_total_wages": 55000,
"line9_total_income": 55000,
"line11_agi": 55000,
"line15_taxable_income": 39250,
"line24_total_tax": 4471.5,
"line33_total_payments": 5200,
"line35a_refund": 728.5
},
"lines": {
"filing_status": "single",
"line1a_wages": 55000,
"line12a_standard_deduction": 15750,
"line15_taxable_income": 39250,
"line16_income_tax": 4471.5,
"line24_total_tax": 4471.5,
"line25a_w2_withheld": 5200,
"line33_total_payments": 5200,
"line34_overpayment": 728.5,
"line35a_refund": 728.5
}
}$55,000 in wages, $15,750 standard deduction, $39,250 taxable income, $4,471.50 tax, $728.50 refund. Every line traces back to the IRS instructions.
# Validate against IRS MeF business rules
opentax return validate --returnId a1b2c3
# Export as IRS MeF XML (ready for e-file)
opentax return export --returnId a1b2c3 --type mef > return.xml
# List entries in a return
opentax form list --returnId a1b2c3
# Update or delete a form entry
opentax form update --returnId a1b2c3 --entryId w2_01 '{"box1_wages": 60000, "box2_fed_withheld": 5800}'
opentax form delete --returnId a1b2c3 --entryId w2_01
# Inspect what fields a node expects
opentax node inspect --node_type w2
# List all registered nodes
opentax node listOpenTax tells you when a new version is available:
$ opentax return get --returnId abc-123
{ ... }
Update available: 0.1.0 → 0.2.0. Run `opentax update` to upgrade.
To update:
opentax updateThat's it. The binary replaces itself with the latest release.
Check your current version anytime:
opentax version131 input nodes covering the full range of 1040 source documents: W-2s, 1099s, all major schedules, credits, capital transactions, and more.
See catalog.ts for the complete list of supported nodes and their schemas. Or from the CLI:
opentax node listThe engine is a directed graph of nodes. Each node is a pure function: validated input in, typed output out. No state, no side effects.
- Schemas defined with Zod, types inferred (never duplicated)
- Immutable data throughout, no mutation anywhere
- Type-safe output routing between nodes enforced at compile time
- 133 real-world benchmark scenarios
AI agents maintain the codebase:
- Read IRS instructions
- Write node implementations
- Generate test cases from official IRS exercises
- Fix regressions
All traced back to the authoritative IRS source.
Requires Deno.
# Run tests
deno task test
# Run accuracy benchmark
deno task bench
# Run the CLI in dev mode
deno task tax return create --year 2025The repo includes four skills that automate the full development lifecycle. Open the project in Claude Code and invoke them with /skill-name.
Run this first. Shows pass/fail counts, pending root causes, and build phase for every form.
/tax-status
Autonomous bug-fixing loop. Reads failing benchmark cases, clusters them by root cause, spawns parallel fixer agents, validates, and commits any net-positive improvements. Loops until all cases pass or progress stalls.
/tax-fix f1040:2025
Sources test cases from IRS publications (VITA exercises, Pub 17, MeF test packages). Run /tax-fix after to see how the engine performs on the new cases.
/tax-cases vita # VITA Pub 4491 training exercises
/tax-cases pub17 # Publication 17 worked examples
/tax-cases "senior with SSA and 1099-R" # free-form scenario
End-to-end form builder. Researches IRS instructions, extracts ground truth, builds all nodes section by section, then runs a validate + fix loop until >= 95% of benchmark cases pass. Resumes if interrupted.
/tax-build 1120
Adding a new form:
/tax-cases f1120:2025 vita # source benchmark cases first
/tax-build 1120 # build nodes, iterate until >= 95% pass
/tax-status # confirm it's green
Fixing a regression:
/tax-status # find what's failing and why
/tax-fix f1040:2025 # autonomous fix loop
Expanding test coverage:
/tax-cases pub17 # pull new IRS examples
/tax-fix f1040:2025 # fix loop against expanded case set
MIT
