Quaderno: tax registration and filing in 50+ countries
The problem. Quaderno covered tax calculation and reporting, but not registration and filing: the part of the tax lifecycle where customers still had to go elsewhere. Sales were declining and we needed more LTV per customer. Filing requires precise manual work, per-jurisdiction expertise and legal responsibility, so operating it in-house was not viable.
What I did. I proposed and validated the hypothesis of working with partners whose core business is filing. We started with manual per-country operation to validate the learnings before building. Then I designed the partner integration model (APIs, data flows, error handling) and the abstractions that captured what countries have in common while isolating what is specific, so adding a country became configuration instead of development, and implemented the integrations myself in the Rails codebase. I acted as the bridge between Sales, C-level and the external partners.
The outcome. In 8 months: hundreds of new tax registrations across 50+ countries, 10x LTV among the customers who adopted it, and the team did not need to scale. Supporting a new market went from weeks to days. It wasn't perfect, though: there's always a country that breaks your assumptions.