Senior full stack engineer

At Sumday, we’re on a mission to make carbon accounting part of the everyday accounting process. Backed by Blackbird other world class investors, we’re building trusted, audit-ready software that lets companies track, manage and report their carbon impact with the same rigour as their financials.

We work with banks, manufacturers, mining companies, major retailers and hundreds of their suppliers and we’re just getting started.

If you’re a senior engineer who wants to ship fast, solve hard problems and build elegant tools that help businesses make better decisions for people and planet, we’d love to chat.

We’re hiring a Senior Full Stack Engineer to help build our platform and shape what’s next.

The Role

You’ll join our tight-knit, high-performance product team (co-founder as Product lead, 2 x designer, QA and 5 other developers) to build and scale the next generation of Sumday’s platform. You’ll work across React/Typescript frontend and a .NET/C# backend.

This role is for someone who’s excited to go deep in product, own technical outcomes and help lay the foundation for what we’re building next, hint: we’re not just a carbon accounting platform. We’re building something bigger, and this is your chance to help shape it from the inside.

What You’ll Do

• Build and scale our core web app with React and .NET
• Own both frontend and backend services and infrastructure for performance, reliability and security
• Design and manage high-quality SQL databases
• Ship features end to end, from discovery to delivery, working closely with design and product
• Help shape technical direction and engineering culture as we grow
• Contribute to our evolving platform architecture with a bias toward simplicity, structure and speed

What You’ll Bring

• 7+ years of full stack engineering experience, ideally in a fast-moving SaaS company
• Strong experience with React and .NET
• Familiarity with modern devops tooling, CI/CD pipelines and agile delivery
• A product mindset, you care deeply about the user and the value you’re creating
• Experience working in small teams or startups where autonomy and initiative are key
• Bonus points for exposure to AI/LLMs, data validation or sustainability data

Benefits

• Competitive salary + equity
• 5 weeks annual leave + 20 weeks paid parental leave
• $1,000/year learning & development budget
• You’ll be part of a mission-driven company at the intersection of accounting, climate and technology — solving real problems for real businesses, and helping shape how the world accounts for impact.