Bank feeds with SimpleFIN

SlowBooks can sync bank transactions automatically using SimpleFIN, an open protocol where you hold the bank credential — not SlowBooks, and not any middleman server we run. There is no SlowBooks cloud in the loop: your machine talks directly to your SimpleFIN bridge over HTTPS.

How it works

1. You sign up for a SimpleFIN bridge — the reference one is bridge.simplefin.org (about $1.50/month, paid by you to them; SlowBooks takes nothing). Any other service that issues SimpleFIN setup tokens works the same way: SlowBooks follows the claim URL inside the token, whatever server it names, as long as it is HTTPS and not a private or local address.
2. On the bridge's site, you connect your bank(s). The bridge handles the bank login, MFA, and aggregation.
3. The bridge gives you a one-time setup token. Paste it into Banking → Bank Feeds (SimpleFIN) → Connect. Connecting, mapping and disconnecting are an administrator's; a bookkeeper runs the syncs.
4. SlowBooks exchanges the token once for a permanent read-only access credential, stored encrypted-at-rest in your company file and never shown again, anywhere.
5. Map each bridge account: the Imports into list offers every bank and credit-card account in your chart, and picking one makes the feed for it when you save the mapping (since 2.31.1). Tick Reverse signs on a feed whose bridge reports money out as positive. Then click Sync Now whenever you want fresh transactions.

Synced transactions land in the same review flow as OFX/CSV imports:

• Duplicates are skipped automatically (dedup on the bridge's stable transaction id, same mechanism as OFX FITIDs) — syncing twice never double-imports.
• Matches are found on arrival — a line whose amount the ledger already has (same side, within five days) is linked to that posting and cleared.
• Bank rules apply on arrival — anything your rules match gets a suggested category. Nothing posts by itself: the account's To review list is where you Add a line (posts it with the category), Match it, or Exclude it; Add all categorised posts the rule-suggested ones in one click.
• Pending transactions are ignored until they post (their ids aren't stable before that).

The first sync reaches back roughly three months; every later sync re-checks a 7-day overlap window before your last sync so late-posting transactions are never missed.

Older history. Fetch older history… reaches back 3, 6 or 12 months (the API takes POST /api/simplefin/sync {"history_months": N}, up to 24). How much there is depends on your SimpleFIN provider: the SimpleFIN Bridge keeps about 90 days, while others, such as BankSync, keep up to a year. The Bridge refuses a request spanning more than 90 days, so SlowBooks asks for the range in slices of 85 days, oldest first; transactions already imported are skipped, and the rest wait in To review like any other line, where anything from before your books began can be excluded.

Trying it without a bank

SimpleFIN publishes a public demo. Generate a demo setup token at beta-bridge.simplefin.org/info/developers and paste it in — you'll get a fake "SimpleFIN Savings" account with sample transactions to play with. Disconnect afterward to clear it.

Notes & troubleshooting

• Setup tokens are single-use. If a connect attempt fails and the token was consumed, generate a fresh token on the bridge site.
• Desktop installs work fully — the sync is outbound HTTPS polling; no webhooks, no ports to open, no server required.
• One source per account. A feed's transaction ids don't match an OFX or CSV export of the same account, so importing both doubles the lines; pick the feed or the file.
• Not too often. The SimpleFIN Bridge asks for 24 or fewer requests a day per token and can disable a token that goes well past that. Each Sync Now is one request; fetching 12 months of older history is about five.
• Payouts from Stripe, PayPal or Square show a Payout… button in To review when the clearing-account option is on (Stripe payments).
• Disconnecting (Banking → Bank Feeds → Disconnect) forgets the credential, mapping, and cache. Transactions already imported stay in your registers.
• Coverage is whatever your bridge supports — the reference bridge covers most US and Canadian institutions.
• If a mapped account stops appearing in syncs, the bank connection usually needs re-authentication on the bridge's site, not in SlowBooks.

Why SimpleFIN and not Plaid?

Plaid requires the application developer to hold API credentials and run a server that proxies every user's bank data. That's the opposite of the SlowBooks design (your data, your machine, no phone-home). SimpleFIN inverts the relationship: each user brings their own credential, and the data flows straight to their computer.