Taimur Abdaal was a data scientist at a London property company when he noticed the thing everyone in finance eventually notices: the numbers that run a business live in spreadsheets nobody fully trusts. He and Lukas Köbis, who would become his co-founder, kept coming back to the same suspicion, that cells and cell references are the wrong building blocks for doing serious work with numbers on a computer.

They did not start with a product. In April 2019 they put a free interactive model on Hacker News asking whether you should buy a house and rent it out, built on the engine they were prototyping. It went to the front page, and Taimur spent the day in the comments answering people about tax treatment, cash flow and simulation methods, ending most replies with an offer to email anyone who wanted to see the real tool. Five years later, announcing the acquisition, he pointed back at that thread and said it gave him and Lukas enough conviction to quit their jobs and work on Causal full time. That post, 20 April 2019, is the anchor this story uses for the start of the clock.

What followed was a long quiet stretch. For the first 18 months Causal was fully self-serve. People signed up, tried it, and disappeared. In his own words the team was stuck in a rut where lots of people thought the product was cool, but nobody was sticking around or paying money. Most users who churn never tell you why, so the feedback loop that was supposed to sharpen the product was mostly silence.

January 2021 is when that changed, and the change was not a feature. Taimur started selling. Instead of letting people sign up and vanish, prospects booked demos on his Calendly link and he talked to them. Because nobody had heard of Causal, the pipeline came from outbound plus introductions through his own network and his investors. He has said they managed to get 40 demos booked for that January, and that roughly 30 prospect meetings a month is a reasonable target for anyone trying this.

Turning meetings into money needed one more move. They offered a free 30 day pilot in which the founders did all the work of getting the customer set up, with success criteria and the price agreed before the pilot started, so there was something concrete to say yes to at the end. That is how the first paying customer arrived: a man called Zach at Smarkets, introduced by Passion Capital, one of Causal's investors, who ended up paying 300 dollars a month on a quarterly contract. Taimur estimates that customer cost about 20 hours of founder time in the first month and roughly 10 hours a month after that, including custom functionality built for that one account. Counting from the April 2019 Hacker News post to that first paid contract, which closed after a 30 day pilot run off the January 2021 demos, the first customer took a little over 21 months.

The price then moved fast, because he made himself move it. Taimur has been open about being terrified to talk about money, saying that before the first sale he had never paid 300 dollars a month for anything himself, so he could hardly believe someone would pay that for Causal. His rule was to quote a slightly higher number on every new deal: 300 became 500, then 1,000, then 1,500, then 2,000, then 3,000 a month within the first year of going to market. His summary of it is that the right price turned out to be about three times what they first assumed, and that many founders stay stuck charging a fraction of what they should.

The pilot structure got lighter as the logos stacked up. After two or three customers there was less to prove, so instead of the heavy free pilots they sold annual contracts with a refund window if the customer was unhappy after 30 or 60 days. That process produced the first ten customers over 2021.

The interesting part is what the sales work did to the product. Every demo told them whether the positioning landed, every question a prospect asked defined the roadmap, and shared Slack channels with each customer turned support into a constant stream of feedback and bug reports. Causal eventually became mostly product-led again, but Taimur has argued it only got there because of the sales-led years. By May 2024 the shape had inverted: a quarter of new customers took a call during their two week trial, and that group signed for 4,200 dollars a year on average against 2,700 for pure self-serve. A third of signups came from word of mouth, a fact the team only discovered after adding a plain how did you hear about us question to the signup form.

On 31 October 2024 Causal was acquired by Lucanet, with the team staying on to run it as its own unit. The price was never disclosed. Asked on Hacker News, Taimur would only say it was more than the two of them could have made at a big tech job over the same five years, and that this middle ground outcome is one more founders should know exists.