Accounting finance ops

Rex

Website
Founded 2026Origin source ↗Checked 2026-09-15

Overview

Rex is a managed AI service for AR and order-to-cash. AI agents and finance experts run the work that delays payment, from collections, portals, disputes and remittances to the shared AR inbox, so cash keeps moving.

Order to cash is a $60B outsourced function because the work is too messy for traditional automation. Every customer has different context, exceptions do not follow clean rules, and the next step is often buried in emails, portals, handoffs, or someone’s memory. Rex agents run continuously in the background and resolve work to SLA standards so cash keeps moving. We're live with pre-IPO tech companies, managing >$500m in receivables from F100 companies, cutting manual follow-up cycles from weeks to hours.

We founded Rex after spending four years building Sequence, an a16z-backed finance ops platform, from zero to Series A — where we saw firsthand that at-scale, O2C still runs on manual labour.

Rex is the #1 winner of the Vercel AI Accelerator out of 2,500 teams, selected by Guillermo Rauch and leaders from OpenAI, Anthropic, Browserbase and more.

Company description As recorded 2026-11-08
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Accounting finance opsAI agentBusinessesEnterpriseSubscription

Founders & team

Merlin Kafka

Founder/CEO

Merlin is the Founder and CEO of Rex, the AI partner for enterprise order-to-cash. He spent 4 years as CPO at Sequence (a16z-backed), an order-to-cash platform where he grew the company to millions in ARR and hundreds of customers. He has deep domain expertise in order to cash and accounts receivable workflows -- the exact space Rex is transforming with AI. Previously a PM at Tessian (Sequoia-backed, acquired in 2023). Studied Industrial Engineering in Cambridge and Product Design in Glasgow.

LinkedIn
Founder profile As recorded 2026-09-15

Lewis Blackwood

Founder/CTO

Founder and CTO at Rex, building the AI partner for enterprise order to cash. Previously: - Founding engineer at Sequence (backed by a16z) - Cofounded Personably (backed by Global Founders Capital) - Early team at GoCardless (YC S11) - Economics at Cambridge

LinkedIn
Founder profile As recorded 2026-09-15
2team members reported
Source-reported As recorded 2026-09-15

Founded 2026 · Source

News & product activity

Sources & observations

Y Combinator

Profile depthenriched profile
Website observationwebsite reachable
Last website check2026-11-11
Location · source statedSan Francisco, CA, USA
Pricing evidenceA pricing page was detected
Maturity: Not assessed · 4 of 6 areas documented

Source-based assessment · automated evidence rules

The retained text does not establish product availability or customer use.

Maturity is an evidence-based assessment, not a success rating. It may understate the current stage where evidence is limited. Coverage records documented areas, not a complete or independently audited company history.

Stage definitions
independent websitesource corroborationreachable websitedescriptive evidenceclassified market and modelsourced peoplesourced founding yearpricing page observed
startup.observe Directory coverage · Sources & method