Rex
<!-- hacklab:yc-profile -- YC company profile AI operations partner for enterprise order-to-cash Rex is a managed AI service for AR and order-to-cash. AI agents and finance expe…
About Rex
YC company profile
AI operations partner for enterprise order-to-cash
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.
- YC batch: Summer 2026
- Founded: 2026
- Team size: 2
- Location: San Francisco
- Country: US
- Status: Active
- Industry: B2B
- Stage: Early
- Tags: B2B, Enterprise, Enterprise Software, AI
- YC partner: Vivian Midha Shen
Founders
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 100+ 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.
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
Source: Y Combinator · Retrieved 2026-11-02. Company information is self-reported on YC.