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SimpleFIN is a paid third-party provider focused on US bank account connectivity. It offers a simpler, more affordable alternative to Plaid for personal finance management.

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How it works

SimpleFIN uses a setup token system to establish secure access to your bank accounts:
  1. Obtain a setup token from SimpleFIN
  2. Sure claims the setup token to get an access URL with embedded credentials
  3. The access URL is used to fetch account data, balances, and transactions
  4. Data syncs automatically to keep your information current

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Setting up SimpleFIN

To connect your US bank accounts:
  1. Sign up for a SimpleFIN account at simplefin.org
  2. Generate a setup token from your SimpleFIN dashboard
  3. In Sure, provide the setup token
  4. Sure will claim the token and establish access to your accounts

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Setup token claiming

The setup token is a base64-encoded claim URL. When you provide it to Sure:
  1. Sure decodes the token to get the claim URL
  2. Makes a POST request to claim the access URL
  3. Receives an access URL with HTTP Basic Auth credentials embedded
  4. Uses this access URL for all subsequent API requests

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Features

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Account syncing

  • Account listing: View all connected accounts with current balances
  • Transaction history: Import transactions with date range filtering
  • Pending transactions: Optional support for pending transactions (varies by institution)
  • Multiple accounts: Connect multiple bank accounts from different institutions

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Date range filtering

When syncing transactions, you can specify:
  • Start date: Fetch transactions from this date forward
  • End date: Fetch transactions up to this date
  • Pending flag: Include or exclude pending transactions
SimpleFIN expects Unix timestamps for date parameters.

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Reliability features

Sure’s SimpleFIN integration includes automatic retry logic:
  • Exponential backoff for transient network failures
  • Up to 3 retry attempts for network errors
  • Handles temporary connection issues gracefully
  • Prevents sync failures from intermittent network problems

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API structure

SimpleFIN uses a simple REST API with embedded authentication:
  • POST /claim: Exchange setup token for access URL
  • GET /accounts: Fetch all accounts with balances and transactions
  • GET /info: Get server information
The access URL contains HTTP Basic Auth credentials, so no separate authentication headers are needed.

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API reference

For detailed protocol documentation, see the SimpleFIN Protocol.

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Pricing

SimpleFIN is a paid service, but typically more affordable than alternatives like Plaid. Check simplefin.org for current pricing.

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Limitations

  • US-focused: Primarily supports US financial institutions
  • Setup token security: Setup tokens can only be claimed once and may expire
  • Pending transactions: Not all institutions return pending transactions, even when requested
  • Rate limits: Subject to SimpleFIN API rate limits
  • Access URL validity: Access URLs can be revoked or expire (returns 403 error)

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Troubleshooting

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Setup token issues

If you receive a 403 error when claiming a setup token:
  • The token may have already been used
  • The token may have expired
  • The token may have been compromised
Generate a new setup token from your SimpleFIN dashboard.

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Missing pending transactions

Some institutions don’t return pending transactions even when the pending=1 parameter is set. This is a limitation of the institution’s data feed, not a bug in SimpleFIN or Sure.

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Network errors

If you experience intermittent sync failures:
  • Sure automatically retries failed requests up to 3 times
  • Network errors are logged for troubleshooting
  • Manual sync attempts may succeed where automatic syncs fail