# Letter AI

Startup profile on Capital Atlas: https://capitalatlas.ai/startups/letter-ai

- Industry: Software
- Headquarters: Chicago, US
- Website: www.letter.ai/
- Total disclosed funding: $53M
- Latest round: Series B (Feb 24, 2026)
- Investors on record: 10

## About

Based in Illinois, US, and founded in 2023, Tractatus AI, Inc. doing business as Letter AI provides artificial intelligence-based solutions for revenue teams helping them with training, coaching, and many others. In February 2026, Letter AI, Inc. raised USD 40 million in series B funding led by Battery Ventures, with participation from Y Combinator, Lightbank, Northwestern Mutual Future Ventures, Stage 2 Capital and Formus Capital.

AI-powered services like training and onboarding, which enable the quick generation of training materials and certification courses, are part of the company's product line. Users may also rehearse sales proposals using realistic scenarios and get immediate feedback that aligns with their company's sales philosophy using AI-powered coaching. 

Additionally, the platform has a tool called revenue co-pilot and content management which provides personalized solutions according to the company and its products.

## Funding rounds

- Series B, Feb 24, 2026, $40M — Battery Ventures, Lightbank, Y Combinator, Stage 2 Capital, Formus Capital, Northwestern Mutual Future Ventures
- Series A, Oct 21, 2025, $11M — Lightbank, Y Combinator, Stage 2 Capital, Formus Capital, Northwestern Mutual Future Ventures, Mangusta Capital
- Seed, May 16, 2024, $2.7M — Y Combinator, Soma Capital Partners, TechNexus Venture Collaborative, Pioneer Fund, Formus Capital

## Investors

- Y Combinator (https://capitalatlas.ai/funds/y-combinator) — Seed, Series A, Series B
- Soma Capital Partners — Seed
- TechNexus Venture Collaborative (https://capitalatlas.ai/funds/technexus-venture-collaborative) — Seed
- Pioneer Fund (https://capitalatlas.ai/funds/pioneer-fund) — Seed
- Formus Capital (https://capitalatlas.ai/funds/formus-capital) — Seed, Series A, Series B
- Lightbank (https://capitalatlas.ai/funds/lightbank) — Series A, Series B
- Stage 2 Capital — Series A, Series B
- Northwestern Mutual Future Ventures — Series A, Series B
- Mangusta Capital (https://capitalatlas.ai/funds/mangusta-capital) — Series A
- Battery Ventures (https://capitalatlas.ai/funds/battery-ventures) — Series B