Senior Data Scientist, Marshmallow
Fraud
2-3 days a week in office (Old Street, London)
We’re building a huge technology company that helps make moving country easier.
Open for applications
We’re building a huge technology company that helps make moving country easier.
501-1000 employees
Open for applications
2-3 days a week in office (Old Street, London)
501-1000 employees
Company mission
To back those who find themselves on a different path, either by choice or by circumstance, helping the exceptions to the rules that others aren’t interested in serving.
Role
Who you are
- You are naturally curious about fraud and interested in how it evolves in the real world
- You care deeply about business impact and think commercially when deciding how to apply your skills
- You are pragmatic about delivery and understand when good enough is better than perfect
- You are a strong communicator and collaborator across both technical and non-technical teams
- Background in fintech, insurance, or similar industries with exposure to fraud or credit risk
- Experience building and deploying ML models that deliver measurable business results
- Experience working with unstructured data (documents, images)
- Understanding of how to evaluate performance within risk decisioning, including performance trade-offs and operational considerations
- Proficiency in Python and SQL and confidence working with large datasets
- At least 3 to 4 years of professional experience in data science or similar roles
Desirable
- Experience working on car insurance fraud or understanding of fraud risks in insurance pricing and onboarding
- Knowledge of industry tools such as Onfido, SIRA, IFB data, or graph-based fraud detection platforms
- Experience deploying fraud solutions into customer-facing products or automated decision systems
- Awareness of how to balance fraud prevention with customer experience and operational efficiency
- Familiarity with document and identity verification processes
- Experience designing, building and deploying Generative AI applications or Retrieval-Augmented Generation (RAG) systems in production environments
What the job involves
- We are here to use data and AI to protect Marshmallow from application fraud, making sure that the people and risks we insure are genuine and fairly priced
- Our work is critical to achieving a healthy loss ratio, unlocking growth, and building trust with under-served customer segments
- Our focus is on policy fraud at the point of sale. That includes detecting misrepresentation, organised fraud such as ghost broking, and verifying customer information efficiently and at scale
- We build models and tools that help Marshmallow validate customer information, automate document reviews, and direct investigative effort to where it has the biggest impact
- The goal is to reduce operational workload while improving decision quality
- You will join a cross-functional team spanning fraud operations, product, and engineering, with full ownership of your initiatives
- You will help shape the next generation of fraud defences powered by intelligent workflows, structured and unstructured data, and a strong focus on experimentation and results
- Success in this role requires deep technical skill, curiosity about fraud behaviours, and the ability to turn insight into action
- Building and deploying models to detect application fraud and misrepresentation, particularly at quote and policy inception
- Using structured and unstructured data including documents and images to automate fraud checks and reviews
- Partnering with product and ops to embed risk-based decisioning and triage into our fraud platform
- Improving how we prioritise fraud reviews through smarter routing / decisioning logic that balances loss ratio impact with operational cost and customer experience
- Evaluating the impact of interventions through A/B tests and automated decision tooling
- Feeding fraud intelligence into model development, working closely with our in-house investigations and analytics teams
- Contributing to the evolution of our fraud infrastructure and helping to shape its use across multiple Marshmallow products
Application process
- Initial call with our Talent Acquisition Partner - 30 mins
- A past experience interview where you will discuss your journey so far and ways of working with Pawel, our hiring manager - 60 mins
- A technical interview with a couple of the team - 90 mins
- A culture interview with a bar raiser to see if your work style fits our processes and values (and vice versa!) - 60 mins
Salary benchmarks
Our take
For many ordinary people, insurance can be inaccessibly expensive. Marshmallow solves this problem by using data and technology to offer fairer coverage for car and van owners.
Car insurers generally quote drivers according to population data, and many drivers are overcharged due to age and demographics. By leveraging data and proprietary technology, Marshmallow can offer more accurate and personalised quotes delivered in minutes, meaning lower fees for drivers. Naturally, this approach has proven popular, with Marshmallow garnering impressive reviews and accolades since it first launched.
The insurtech space is becoming increasingly competitive, and more and more tech companies are moving into the car insurance space, so the company is currently looking to expand into other insurance areas as it grows into a multiproduct scale-up fintech company. Marshmallow’s unicorn status and doubling of profit since 2023 are clear indicators of the company’s ongoing success and scalability, and will help to facilitate this diversification.
For now, the company is focused on helping those outside the norm, such as those who have uprooted their lives and moved to the UK. But in the future, it hopes to expand to any group of people who are unfairly marginalised and whose problems Marshmallow is uniquely positioned to solve.
Kirsty
Company Specialist at Welcome to the Jungle
Insights
Company
Employee endorsements
Open and honest communication
"At Marshmallow information is 'over-shared' and this starts from the CEOs and continues through the organisation. People across the business are..."
Funding (last 2 of 5 rounds)
Apr 2025
$90m
SERIES C
Sep 2021
$83m
SERIES B
Total funding: $208.2m
Company benefits
- Flexible working - Manage your own time flexibly. Just make sure your team is happy too.
- Ben benefits - Get your hands on your flexible benefits budget with the Ben Mastercard and spend it wherever you want.
- Competitive bonus scheme - designed to reward and recognise high performance 🌟
- Private healthcare - We want to support everyone’s wellbeing at Marshmallow, which is why we offer private healthcare insurance with Vitality.

- Cycle to work scheme - We’re registered under the Cycle-to-Work scheme, so you can buy a new bike tax-free. Lycra shorts optional.
- Mental wellbeing - We have partnered with Oliva to offer mental health support and make therapy sessions more accessible.
- Learning and training - Personal budgets for books and training courses to help you grow in your role. Weekly book clubs and learning sessions. Plus 2 days a year - on us! - to further your skillset.
- Company socials - We give all of our teams monthly budgets to get to know each other better outside of work. Plus we have company-wide socials every two weeks, themed parties, and more.
Company values
- We are relentless
- We are bold
- We are challenging
- We have no ego
Company HQ
Old Street, London, UK
Articles
Leadership
Oliver Kent-Braham
(Co-CEO)Previously worked in Growth & Partnerships at Yoti and Leveraged Finance at Investec. Previously founded Reel Money.
Alexander Kent-Braham
(Co-CEO)Previously worked in Product at Yoti. Also co-founded Reel Money and was an Analyst at hedge fund QCM.
People progressing
Joined as Software Engineer, being promoted to Technical Team Lead after 10 months and now Staff Engineer.
Diversity, Equity & Inclusion at Marshmallow
- To solve big problems, we need exceptional people from all walks of life. We're creating a culture where everyone feels empowered to bring their unique perspectives and boldest ideas to the table. Belonging - As a community, we foster an environment where everyone feels supported and safe to bring their authentic self to work. Recognition - We recognise and celebrate the differences in our experiences, understanding that our unique contributions help us collectively deliver our best work. Influence - We’re empowered to share our voice and have influence. We value diversity of thought, knowing we are better through our collective perspectives and experiences.
Share this job
View 29 more jobs at Marshmallow