Rex YC Application

Summer 2026Active

Rex went through Y Combinator in the Summer 2026 batch as a B2B company. Below: what the company does, who founded it, and its application to YC, reconstructed question by question in the real YC form.

YC batch: Summer 2026
Industry: B2BFinance and Accounting
Team size: 2
Status: Active
Launched: 2026

Founders

Lewis BlackwoodFounder
Merlin KafkaFounder

What Rex does

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.

Rex's YC application, reconstructed

Y Combinator application

Rex, Summer 2026 batch. The real form questions, answered from public data.

Founders2
Company7
Progress7
Idea4
Equity3
Curious2
Batch Preference1

Company

Company name

Rex

Describe what your company does in 50 characters or less.

AI Operations Partner for Enterprise Order to Cash

What is your company going to make? Please describe your product and what it does or will do.

We built an AI-native service that continuously manages the order to cash process for enterprises. Rex agents handle invoices, customer communication, and exceptions in the background, reducing manual follow-up from weeks to hours. This replaces manual, people-heavy operations in a $60B market that traditional automation can't handle due to messy, exception-heavy workflows.

Where do you live now, and where would the company be based after YC?

We live in London, United Kingdom, and plan to keep the company based here after YC.

Explain your decision regarding location.

We're based in London because that's where we started building Rex and where our early users are. It makes sense to stay close to our customers and continue building here rather than relocate after YC.

21 more answers in the full application

Founders, Progress, Idea, Equity, Curious, Batch Preference are in the full version. Create a free account to open it in YC Insights, next to every other YC batch.

See full application

Frequently Asked Questions

Is this the real Rex YC application?

No. Y Combinator keeps submitted applications private. This is a reconstruction: the real YC form questions, answered from Rex's public data (launch notes, founder backgrounds, product description). It shows how a company like Rex would present itself to YC, not the text they submitted.