Monarch Money

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Do not build this. The bank connections are a licensed relationship, not an API key.

Reading account data requires an aggregator with regulatory permission and contracts with the banks, which you cannot enter as an individual. That is the product; everything else is a budgeting application.

WHAT TO DO INSTEAD
- Keep it if automatic connections are why you use it
- If you would rather your financial history never left your own machine, build the version below and import instead of connecting

WHAT YOU CAN BUILD, AND SHOULD

STACK
- Node 20+ with Fastify, SQLite through better-sqlite3, a PWA for the phone
- Everything local, encrypted at rest, sent nowhere

WHAT TO IMPLEMENT
- Import from each bank's own export — CSV, OFX, QIF — with a mapping step, a dry run, and duplicate detection by a stable import identifier then by date, amount and payee. A double-imported month is the classic disaster
- Amounts in integer cents with a currency. Never a float
- Payee normalisation: one shop appears as six strings across a year, and collapsing them is most of what makes categorisation work
- Rules learned from your corrections — a payee pattern to a category, suggested first and automatic once confirmed
- Balances derived from transactions at query time, never stored
- Reconciliation against the bank's stated balance, which is the only thing that tells you the data is right
- Net worth over time, spending by category, and a comparison against previous months

AND THE ONE IDEA WORTH TAKING FROM THE OTHER SIDE OF THIS CATEGORY
Assigning money you already have a job, rather than forecasting a month, is a genuinely different way to budget and the reason people stick with it. That method is described under YNAB elsewhere in this catalogue, and it costs nothing to adopt.

THE ONE THING TO GET RIGHT
This is a complete record of your financial life. Encrypt it, keep it local, back it up encrypted off the machine, and put no analytics in it. Not one event.

THE ONE-LINE VERSION
The connection is licensed; everything else is a fortnight. Import by hand and keep it on your own machine.