The entire front-end of an e-invoicing SaaS.

E-invoicing is becoming mandatory for French companies. The Melrys back-end was already well under way; the front-end was a set of fragments with no owner. I came in to take full responsibility for it.

The domain does not forgive approximation: one miscalculated invoice or one wrong transmission status, and it is the end client who has a problem with the tax authority.

On an invoicing product, a bug does not cost you a ticket. It costs you the trust of an accountant who will not come back.

• 30 to 60 screens built pixel-perfect from the Figma mockups
• React architecture rewritten into a modular structure, organised by business domain
• REST API integration with Zustand state management
• End-to-end tests on the critical journeys: creating, sending and tracking an invoice
• REST API testing before integration (Postman, cURL)
• Systematic reporting of gaps between mockups and business logic

1. 01Delivered on the planned date, despite a complete redesign of the mockups mid-project.
2. 02A visible drop in production bugs on the journeys covered by tests.
3. 03The modular architecture adopted by the team as the standard for the rest of the product.