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Building the workforcefor order to cash.

Rex is built by a small team in London and San Francisco. We spent four years in order-to-cash software before starting it.

Why we’re building Rex

Rex is an AI company that automates finance operations in global enterprises.

Somewhere right now, a finance team is copying data from a portal into a spreadsheet into an ERP.

This is the reality of operational finance work in most enterprises. People operating across different systems, email chains, portals, spreadsheets, stitching together context that lives in different places. The work requires judgment every time and most of the knowledge lives in someone’s head.

This is why people have been the only way to scale as volume increases.

So why have existing automation tools and ERPs not solved it? We know this firsthand. We spent four years building order to cash and AR software and working with hundreds of finance teams.

Rule-based automation can’t handle the exceptions, the judgment calls, the context hunting. Systems of record don’t hold enough context beyond their own perimeter.

Why open individual apps and use disconnected AI tools with limited context when you can delegate the work to agents that operate across all of them?

Rex is the agentic finance platform that connects to your existing stack and executes work end to end – collections, reconciliation, portal uploads and more – no migration required. Finance teams using Rex become process architects and managers of agents. With Rex, teams can delegate work that requires context from different systems to a suite of competent finance agents.

Rex agents augment finance teams, route sensitive cases for approval, and operate within an auditable governance layer enterprise finance requires. Over time, this decision layer becomes the institutional memory that today lives in people’s heads and conversations. As finance teams adopt more agents, whether from us or built internally, they can draw on the accumulated decision context to inform new agents, with governance infrastructure that ensures every action is fully auditable.

The repetitive execution and context switching that consume finance teams today will get absorbed by AI. What remains is initiating strategic work and approving outcomes. The reason most finance people enter the profession in the first place.

Merlin Kafka & Lewis Blackwood

Founders, Rex
Founders

We spent four years inside this problem,building order-to-cash software for finance teams.

Billing engine
Billions in receivables processed
ERP integrations
50+ completed, NetSuite & beyond
Receivables automation
AR run for hundreds of finance teams
Revenue recognition
Built ASC 606 software for SaaS
Merlin Kafka

Merlin Kafka

Co-founder & CEO

Previously CPO at Sequence (a16z). Before that, led product at Tessian (Sequoia, acquired by Proofpoint), building enterprise AI security for banks and law firms.

Studied industrial engineering at Cambridge.

LinkedIn
Lewis Blackwood

Lewis Blackwood

Co-founder & CTO

Led engineering at Sequence as one of its first hires. Earlier, early engineer at GoCardless (Accel) and founder of Personably (GFC-backed).

Studied economics at Cambridge.

LinkedIn
“Four years in this space taught us one thing: everything is an edge case. Because every customer’s AR and AP team operates differently. The real work is the judgment that happens between systems. That is what we built Rex to carry.”
Merlin KafkaCo-founder & CEO
Background

How we got here.

Before Rex

We built Sequence, billing and CPQ for SaaS, from zero to Series A. Four years scaling a billing engine that processed billions in receivables, with 50+ ERP integrations and hundreds of finance teams.

The turn

Those years showed us why automation kept falling short. Rule-based tools can't handle the exceptions, the judgment calls, the context hunting. Agents that operate across systems can.

Rex today

Rex runs AR operations for scaled technology companies. Backed by Y Combinator, and selected #1 of 2,500 teams in the Vercel AI Accelerator.

Backed by

Y Combinator
VercelVentures

And leaders from

Stripe
Coinbase
McKinsey
Browserbase
Braintrust
Cursor

Partners

NVIDIA
Deloitte
AWS

Come seewhat we're building.

Rex runs the manual O2C work your team would otherwise outsource.

Join the team