opentax

Filed Open Tax software

opentax.filed.com - 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.

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Why

• 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.

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Use with AI agents

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.

Claude Code

If you use Claude Code, install OpenTax as a plugin so the skill is always available:

1. Add the marketplace:

/plugin marketplace add filedcom/opentax

2. Install the plugin:

/plugin install opentax@opentax

3. 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

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Install CLI

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

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Example: single W-2 filer

$ 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.

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More commands

# 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