About this role
**AI Transformation for Enterprise Finance**
Rex builds AI agents for enterprise finance, starting with order to cash. Our customers delegate a process to us, and we run it with agents while finance experts oversee the work. Our agents operate across email, ERPs and customer portals to resolve payment blockers and help businesses get paid.
We’re building agents that can take responsibility for complex financial workflows: reason over messy data, handle exceptions and improve through feedback from finance experts. The challenge is earning the trust to act autonomously in operations that affect real money.
**Who we are**
Rex was founded in 2026 by Merlin Kafka (CEO) and Lewis Blackwood (CTO).
Merlin previously served as CPO at Sequence (a16z) and PM at Tessian (Sequoia), and studied industrial engineering at Cambridge. Lewis previously led engineering at Sequence, joined GoCardless early and founded a startup backed by GFC. He studied economics at Cambridge.
Our team brings years of experience building AI and finance products and working with hundreds of finance teams. We know this domain inside-out.
Rex is global from day one and operates across San Francisco and London.
**What you’ll do**
You’ll be the team’s subject matter expert on order to cash and help run customer operations alongside Rex’s agents. You’ll bring practical knowledge of billing, collections, cash application and reconciliation into how we build the product and configure agents for each customer.
Day to day, you’ll review and approve agent actions, handle exceptions and resolve cases that need human judgment. You’ll work closely with customer finance teams to understand their policies, investigate payment blockers and keep the work moving.
You’ll turn what you learn into clearer procedures and better agent behaviour, working directly with engineering.
**You’ll fit if you**
* Have around 2-3 years of hands-on experience in order to cash, AR or credit control, ideally at enterprise scale.
* Are comfortable with customer ledgers, payment allocation, reconciliation and ERP systems.
* Can work through complex cases and explain your reasoning clearly to customers and engineers.
* Use AI tools confidently and want to help shape how agents run finance operations.
This role is an ideal fit for an AI-native operator who spent the last few years working in order to cash or AR at enterprise scale and now wants to put their domain knowledge to work.
This role is full-time in-person in London.