A personal bookkeeping application "decompiled" from the ashes of QuickBooks 2003 Pro.

Free and open source. Runs on Windows, macOS, and Linux. No Intuit activation servers required.

Get started: docker compose up — see INSTALL.md for all install options.

Ships with both themes — toggle from the topbar or hit Alt+D. Choice persists in localStorage, so reloads stay in the theme you picked.

I ran QuickBooks 2003 Pro for 14 years for side business invoicing and bookkeeping. Then the hard drive died. Intuit's activation servers have been dead since ~2017, so the software can't be reinstalled. The license I paid for is worthless.

So I built my own replacement. I transferred all my data from the old .QBW file using IIF export/import.

The codebase is annotated with "decompilation" comments referencing QBW32.EXE offsets, Btrieve table layouts, and MFC class names — a tribute to the software that served me well for 14 years before its maker decided it should stop working.

This is a clean-room reimplementation. No Intuit source code was available or used.

Full payroll & HR module — Onboarding checklists, time tracking, PTO policies and requests, deductions (401k, health, HSA), court-ordered garnishments, W-2/W-3/940/941 generation, and a token-accessed employee self-service portal for pay stubs, W-4 updates, direct-deposit setup, and time-off requests.

Analytics dashboard + AI Insights — KPI cards plus four charts (12-month revenue line, expenses doughnut, A/R+A/P stacked bar, 90-day cash forecast), MTD/QTD/YTD period selector, CSV/PDF export with branded headers. Optional one-shot executive brief and 11 curated predefined analyses via bring-your-own-key for any of seven providers (xAI Grok, Groq, Cloudflare Workers AI, Anthropic Claude, OpenAI, Google Gemini, or a self-hosted Cloudflare Worker gateway); keys encrypted at rest.

Inventory & reporting — Perpetual-inventory ledger with weighted-average cost, automatic COGS journal entries, click-through drill-down on P&L and Balance Sheet rows, fuzzy duplicate detection on customer/vendor names, and Saved Reports for one-click reruns.

Customer details popout + reseller permits — Click a customer row for a single-screen details modal with addresses, autosaving notes, attached reseller permits, and recent invoices/payments. A standalone reseller-permit module tracks expiration, validates per-state formats (WA 9-digit, CA 9-12, TX 11), and one-click-opens the state's official lookup site in your default browser for verification — the verification trail (who, when) is stored locally.

Hardened for production — App-level HTTPS redirect + HSTS, Content-Security-Policy, Fernet at-rest encryption with versioned ciphertext (clean key rotation), portal token expiration (90-day idle + 1-year hard), Argon2id passwords, rate limiting on login and portal, and startup checks that fail hard on critical misconfig. See docs/security-hardening.md.

See CHANGELOG.md for the full release history.

A few things in here that aren't normal for self-hosted bookkeeping.

Cryptographically tamper-evident tax forms. Every W-2, W-3, Form 940, and Form 941 PDF carries a SHA-256 content hash and an audit ID printed in the footer. Hand the printout to an auditor and they can recompute the hash, look it up against the local document_audits chain, and confirm the form hasn't been edited since you generated it. Not a watermark — a verification trail.

Bring-your-own-AI, including your own gateway. AI Insights and 11 predefined analyses run against any of six hosted providers (xAI Grok, Groq, Cloudflare Workers AI, Anthropic Claude, OpenAI, Google Gemini) — or, as the seventh option, against a Cloudflare Worker you host yourself, so the prompt never leaves infrastructure you control. API keys are encrypted at rest with Fernet under a versioned ciphertext you can rotate without downtime.

One-click reseller-permit verification. Type a customer's permit number — we validate the per-state digit pattern inline (WA 9-digit, CA 9–12, TX 11). Click Verify and your default browser pops the state's official lookup page; whatever you decide gets stamped onto the customer record as a who-and-when verification trail. No fake API integration that breaks in six months — just the workflow done right, with the digital permit encrypted at rest and the expiration date on the dashboard reminder strip.

Boots refuse to lie to you. Dev and debug containers run the wiring audit before uvicorn binds the port — if the JS bundle drifted from the Python routes (route renamed, container built off a stale checkout), the container fails to start instead of 404-ing mid-feature. Release images are gated by the same check in CI before they're ever built.

Full feature catalog (300+ entries across every module) lives in docs/features.md. Highlights:

• Accounts receivable — Invoices, estimates, payments with multi-invoice allocation, credit memos, recurring schedules, batch payments, Quick Entry for paper backlogs.
• Accounts payable — Purchase orders, bills (with vendor default expense accounts), bill payments, AP aging.
• Double-entry accounting — Manual + auto journal entries, 50-account Chart of Accounts (Contractor template), closing-date enforcement, real-time balance updates, automatic audit log via SQLAlchemy event hooks.

• Banking — Bank register with running balance, deposits, credit-card charges, check printing (3-per-page), full reconciliation workflow, OFX/QFX import with FITID dedup.
• Reports & tax — P&L, Balance Sheet, A/R & A/P Aging, General Ledger, Sales Tax with pay-to-government flow, Customer Statements, Schedule C export.
• Payroll & HR — Full module with tax forms; see docs/payroll-hr-module.md.
• Analytics + AI — Real-time BI layer with 8 metrics and a 90-day cash forecast; optional BYOK AI Insights layer. Full feature reference in docs/features.md.
• Inventory — Perpetual-inventory ledger, automatic COGS, weighted-average cost, reorder points, valuation, manual adjustments.

• Duplicate detection — Fuzzy match on customer/vendor names (difflib ≥ 0.85 after normalizing case, punctuation, and business suffixes like "Inc"/"LLC"). The form shows the matched names + similarity %; you confirm-and-create-anyway or back out.

• Online payments — Stripe Checkout integration. See docs/setup-stripe.md.
• QuickBooks Online sync — OAuth + bidirectional sync. See docs/setup-qbo.md.
• QB2003 interop — IIF import/export with type-mapping, validation, and round-trip safety.

git clone https://github.com/VonHoltenCodes/SlowBooks-Pro-2026.git
cd SlowBooks-Pro-2026
docker compose up

Open http://localhost:3001. PostgreSQL, migrations, and seed data are handled automatically.

For native installs (Linux + macOS), demo data, troubleshooting, and CORS / port-change recipes, see INSTALL.md.

For backups, restore, key rotation, and monitoring see docs/operations.md. For a production-launch checklist see docs/release-checklist.md.

Python 3.13 + FastAPI on PostgreSQL 17 (SQLite for tests) with SQLAlchemy 2.0 and Alembic migrations. Vanilla HTML/CSS/JS single-page app — no framework, no build step. WeasyPrint + Jinja2 for PDFs. Self-hosted Chart.js for analytics (no CDN; LAN-deployable). Stripe Checkout for online payments. python-quickbooks + intuit-oauth for QBO sync. Runs on port 3001 by default.

Full project layout in docs/development.md.

Source Available — Free for personal and enterprise use. No commercial resale.

You can use, modify, and run Slowbooks Pro for any personal, educational, or internal business purpose. You cannot sell it or offer it as a paid service. See LICENSE for full terms.

• 14 years of QuickBooks 2003 Pro (1 license, $199.95, 2003 dollars)
• IDA Pro and the reverse engineering community
• The Pervasive PSQL documentation that nobody else has read since 2005
• Every small business owner who lost software they paid for when activation servers died

• VonHoltenCodes — Creator
• PNWImport — Security hardening (auth, CORS, path traversal, atomic writes, non-root Docker, rate limiting), analytics engine, AI insights with 7-provider support, Cloudflare Worker gateway, inventory ledger, drill-down reports, fuzzy duplicate detection, saved reports, payroll/HR module, tax-form audit chain, reseller-permit module, customer details popout
• jake-378 — Backup UI fixes, report period selectors, invoice terms autofill, date validation fixes
• WC3D — Jinja2 XSS security fix