Cairn

Bookkeeping and CRA set-aside tracking for Canadian self-employed people. Cairn records income and expenses in form T2125 categories, tracks GST/HST, and estimates income tax and CPP/QPP owing as you go, so freelancers know how much of each payment to put away.

What's in this version

• Set-aside estimate: 2026 federal and provincial brackets, CPP or QPP for the self-employed, and GST/HST owing
• Entries: income and expenses with T2125 lines, business-use %, and the 50% meals rule
• Receipt reading: describe a purchase or upload a photo; Claude fills in the form for review
• Home office and equipment: business-use-of-home with carry-forward, and capital cost allowance (CCA) by class
• GST/HST: regular and quick methods, the $30,000 registration meter, and a quick-method savings hint
• Tax time: T2125 and GST/HST return summaries, CRA deadlines, and a CSV export for an accountant
• Privacy: every table and the receipts bucket are protected by Postgres row-level security

Stack

Next.js 15 (App Router, server actions) · Supabase (Postgres, auth, storage) · Claude API for receipts · Tailwind CSS 4 · Vitest. Bank feeds (Flinks) and billing (Stripe) are planned; see docs/ROADMAP.md.

Getting started

1. Create a Supabase project, then apply the schema:

   npx supabase link --project-ref <your-ref>
   npx supabase db push
   

   Or paste supabase/migrations/0001_init.sql into the SQL editor and run it. 0002_receipts_storage.sql is optional for now (photo storage is not used yet).
2. In Supabase → Authentication → URL configuration, add http://localhost:3000/auth/callback as a redirect URL.
3. Configure the app:

   cp .env.example .env.local   # fill in the Supabase URL and anon key, and an Anthropic API key
   npm install
   npm run dev
   

4. Open http://localhost:3000 and sign in with a magic link.

Receipt reading is hidden when ANTHROPIC_API_KEY is not set.

Scripts

Command	What it does
npm run dev	Start the dev server
npm run build	Production build
npm test	Unit tests for the tax engine and receipt schema
npm run test:db	Applies the migrations to an in-memory Postgres and checks row-level security
npm run typecheck	TypeScript check

Project layout

src/lib/tax/          Pure tax engine: rates, brackets, CPP/QPP, GST/HST, CCA, summaries, deadlines
src/lib/data.ts       Loads a user's books from Supabase and maps rows to tax-engine types
src/app/(app)/        Signed-in screens and their server actions
src/app/api/receipts  Claude receipt extraction (structured output)
src/app/api/export    Accountant CSV
supabase/migrations   Schema and row-level security policies

The tax engine has no I/O, so it can be tested on its own and reused in a mobile app.

Tax figures

The 2026 reference figures live in src/lib/tax/reference.ts. Some provincial figures are still estimates; docs/TAX_REFERENCE.md lists what has been checked and what has not. Cairn gives estimates for planning and is not tax advice.