(Senior) Machine Learning Engineer - Chat & GenAI UK - Remote

About Cleo

At Cleo, we're not just building another fintech app. We're embarking on a mission to fundamentally change humanity's relationship with money. Imagine a world where everyone, regardless of background or income, has access to a hyper‑intelligent financial advisor in their pocket. That's the future we're creating. Cleo is a rare success story: a profitable, fast‑growing unicorn with over $300 million in ARR and growing over 2× year‑over‑year. This isn't just a job; it's a chance to join a team of brilliant, driven individuals who are passionate about making a real difference.

About the role

(Senior) Machine Learning Engineers at Cleo work on building novel solutions to real‑world problems. This really does vary but could be: creating chatbots to coach our users around their financial health, creating classifiers to better understand transaction data or even optimising transactions within our payments platform. Ultimately, we’re looking for a brilliant (Senior) Machine Learning Engineer to join us on our mission to fight for the world's financial health.

You’ll be leading technical work within a team of adaptable, creative and product‑focused engineers, who train & integrate cutting‑edge machine learning across a variety of products and deploy them into production for millions of users. We understand our customers, we understand their pain, and we are passionate about helping them.

What you'll be doing:

• Training and fine‑tuning models to solve customer problems across our chatbot and the bank transaction data behind it.
• Deploying these models into our production environments using our in‑house ML platform.
• Working cross‑functionally with backend engineers, data analysts, UX writers, product managers, annotation teams, and others to ship features that improve our users’ financial health.
• Taking the initiative to propose & lead technical work towards problems that were previously unknown or poorly understood.
• Driving change at the chapter level that affects multiple squads.
• Keeping Cleo at the forefront of NLP by driving the adoption of appropriate state‑of‑the‑art techniques and communicating the team’s successes and learnings at the company level & beyond.
• Mentoring & advising colleagues on their choices of models, architecture, and evaluation, promoting best practices for how we use LLMs.

Here are some examples, big and small, of the kinds of product feature work our ML Engineers have taken part in over the last year:

• Building AI Agents to explore and derive insights from users transactional data.
• Developed deeper understanding of users finances through models extracting meaning from transactional data.
• Developed contextual intent classifiers to understand what conversations users are having with Cleo, enabling control of how Cleo should respond.
• Built ML models to understand the actions that users have available to them in Cleo and provide those contextually in conversations.
• Built ML models to understand the risk of customers using bank transaction features and user activity.
• Built models to optimise the payment success for our customers and optimising the costs for the business.

Whatever problem you tackle, and whichever team you join, your work will directly impact those most in need, helping to improve their financial health.

What You'll Need:

• Excellent knowledge of both Data Science (Python, SQL) and production tools.
• A deep understanding of probability and statistics fundamentals.
• Big picture thinking to correctly diagnose problems and productionising research.
• Top tier communication skills, to be able to partner with Product and Commercial Leaders.
• Industry‑leading contributions to your field, communicated through conferences, blogs, talks, or open‑source projects.
• Advanced Degree in a quantitative discipline or equivalent commercial experience.

Nice to have:

• Strong experience with additional programming languages, such as Java, Scala, C++.

What do you get for all your hard work?

• A competitive compensation package (base + equity) with 3‑annual reviews, aligned to our termly OKR planning cycles.
• Work at one of the fastest‑growing tech startups, backed by top VC firms.
• A clear progression plan. We want you to keep growing.
• Flexibility. We can’t fight for the world’s financial health if we’re not healthy ourselves.
• Company‑wide performance reviews every 4 months.
• Generous pay increases for high‑performing team members.
• 25 days annual leave a year + public holidays (+ an additional day for every year you spend at Cleo, up to 30 days).
• 1 month paid sabbatical after 4 years at Cleo.
• 6% employer‑matched pension in the UK.
• Private Medical Insurance via Vitality, dental cover, and life assurance.
• Online mental health support via Spill.
• Enhanced parental leave.
• Workplace Nursery Scheme.
• Paid for access to multiple AI platforms.
• Access to the latest AI coding models.
• Pick your kit - choose between a Windows or an Apple computer.
• Regular socials and activities, online and in‑person.

We strongly encourage applications from people of colour, the LGBTQ+ community, people with disabilities, neurodivergent people, parents, carers, and people from lower socio‑economic backgrounds.