Bill.com (Accounting) and Mollie (Payments) are commonly run side-by-side. When teams operate both, the question that follows is always how to keep the two in sync without re-entering data twice.
What people typically integrate
- Match incoming payments to invoices automatically
- Reconcile processor fees as separate journal entries
- Push refunds and disputes back into accounting for visibility
- Generate sales tax breakdowns at deposit time
How the integration works
There are usually a few paths to choose from, depending on stack and budget:
- Native integration (one or both vendors offer first-party support)
- rest-api" class="glossary-link text-db-cyan hover:text-db-cyan-dark underline decoration-dotted underline-offset-2" title="Representational State Transfer - an architectural style for building web services....">REST API + scheduled sync (build once, run on cron)
- Webhook-driven sync (real-time, event-based)
- Zapier / Make / n8n (low-code, fast to ship, ongoing per-task fees)
- Custom Python / ORM, admin interface, authentication, and 'batter...">Django adapter (full control, no per-task fees, requires engineering)
What flows between the systems
Common records that move back and forth:
- transactions
- payouts
- fees
- refunds
- disputes
Complexity
This integration is typically simple. Both tools have native or first-party support for each other, and a working integration is mostly configuration rather than custom development.
Need help building this?
Purcell Analytics builds custom integrations between Bill.com and Mollie for businesses that want this running reliably without DIY headaches. Schedule a consultation to talk through your specific use case.