The foundation underneath every module.

Every business in TwinBooks runs as its own Client with isolated data. There's no shared customer table that could accidentally leak records between tenants — isolation is enforced at the data layer, not at the application layer where it's easy to slip up.

If you have access to multiple businesses (say, you're the owner of two companies, or an accountant managing several clients), you can switch between them without signing out. Each switch loads only the records you have access to in that tenant — users, customers, invoices, banks, everything.

Roles ship in three flavors: Owner, Admin, and Accountant, with per-module fine-grained controls layered on top. Read-only accountant access is a single click.

Every create, update, and delete is captured in the audit log with who, what, when, and the resource it touched. The full body is captured (with sensitive fields like passwords and tokens redacted) so you can answer “what changed and when” without guessing.

That's the difference between an answer and a hunch when an auditor asks why a $4,200 deposit was reapplied to a different invoice three months later.

TwinBooks installs to your phone's home screen with no app store, no install friction, and no review delay:

• One-tap install on iOS Safari and Android Chrome. Full-screen, branded, looks native.
• Instant repeat opens thanks to a service worker that caches your shell, fonts, icons, and translations.
• Offline-resilient. Pages you've already visited still load without a signal; new pages show a graceful offline notice.
• Same codebase as the web app. Every fix and feature ships everywhere at once.
• Tenant-safe. Bank data, customer records, and payroll responses are never cached on shared devices.

• Locked-down API with helmet headers, CORS allowlist, and tiered rate limiting on auth endpoints
• Schema-validated requests — typed payloads checked before they touch the database
• Idempotent integrations — Stripe webhooks, Plaid sync, Gusto syncs, and seed data all safe to re-run
• 169 automated tests covering authentication, RBAC, every CRUD module, payment workflows, audit logging, and Stripe webhook signature verification
• Bank-grade Plaid integration with read-only tokens — TwinBooks never sees your banking password
• SOC 2 partner ecosystem — Plaid, Gusto, and Stripe all carry their own SOC 2 Type II attestations