Rex (YC S26) — AI-native BPO for enterprise order-to-cash
Rex is an AI-native service for order to cash. Rex replace manual operations with AI agents that continuously manage invoices, customers and exceptions.
Rex is a Y Combinator company in the Summer 2026 batch. Its directory entry describes it as: AI-native BPO for enterprise order-to-cash. The founders listed are Merlin Kafka (Founder/CEO), Lewis Blackwood (Founder/CTO) (Y Combinator directory entry, May 27, 2026).
Sell to companies like these? Paste your website and see 10 with a filed reason to buy this month. Free.
Opens in a new tab. No signup.
What it does AI-native BPO for enterprise order-to-cash (source)
Example from a real report (our sample on Target): “In March 2026, Target announced a planned incremental $1 billion operating investment” Source: Target Corporation (press release)
Rex is an AI-native service for order to cash. Rex replace manual operations with AI agents that continuously manage invoices, customers and exceptions.
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.
What the site is built with
Next.jsframeworkVercelhosting
Read from the page's own HTML and response headers on 10 September 2026, at https://www.rex.inc/. Each badge matched a string the site serves about itself — hover one to see which. Nothing here is a traffic, ranking or revenue figure: those cannot be read off a page and are not claimed.
Checked away from the directory entry. What is below does not come from the company's Y Combinator page.
Rex is the AI operations partner for order-to-cash. Its agents cover every account and resolve exceptions before cash gets stuck.
The title and description the site itself served, answering 200. Not a cached copy and not the company's directory entry — what was live when we asked.
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.
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
Founders, titles and bios as the company published them. Photographs are our own copies of the ones on that record, so they do not break when the original link expires.
One of 142 companies held here in B2B › Finance and Accounting.
No investor is drawn from a Form D — the form states how many invested and never who. The one investor on this graph is named because a batch has exactly one.
Want the whole picture on Rex?
Example from a real report (our sample on Target): “In March 2026, Target announced a planned incremental $1 billion operating investment” Source: Target Corporation (press release)
A Full Report on Rex: verified, sourced, every claim cited, ready in a few minutes. See pricing.
What the Full Report on Rex covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
Sources
7 cited sources found
Plus the sections for what you are deciding, which you pick after ordering.
You get an alert in MentionFox the next time this company shows up.
Is this you?
If you're behind Rex: acceptance into a YC batch is one of the few weeks a young company gets looked up by people who matter — investors, other founders, press. FoxPlug turns the commits, deploys, and releases you're already making into that story automatically, so anyone who looks finds something current. GetFoxChat puts a guide on your own site so the people YC's own page just sent you don't read one line and leave.
