SumUp Accelerator – Software Engineer Intern

Build real products that help millions of small businesses thrive.

At SumUp, we build fintech tools that empower over 4 million merchants across 37 markets to run and grow their businesses. The Warsaw Accelerator Program puts you at the heart of that mission - working on real product challenges in the Sell Online domain, from reducing merchant onboarding friction to building AI-powered tools that save merchants time and drive revenue.

This isn't a traditional internship. From day one, you'll join a small product team, take real ownership of a problem, and ship a working MVP alongside experienced engineers and product mentors. The top three performers will be offered a one-year contract at the end of the programme.

📍 Location: Warsaw, Hala Koszyki (office-first)
⏱  Duration: 3 months, 15th July – 15th October 2026 (full time)
💰 Salary: 8,000 PLN gross per month (Civil Law Contract / Umowa Zlecenie)

Curious what that actually looks like? Watch how our Accelerator participants become contributors to real-world features at SumUp.

What you'll work on

You'll join one of two teams tackling real merchant problems, including:

• Reducing onboarding friction by automating merchant setup and data import
• Building smart waitlist and re-engagement tools to help merchants fill gaps and grow revenue
• Exploring a consumer-facing marketplace where customers can discover and book services from SumUp merchants
• Developing AI-powered tools - including a voice-based AI receptionist and a conversational merchant assistant

Your impact

Working alongside engineering mentors, product leads, and experienced SumUppers, you'll:

• Design, build, and ship a functional MVP addressing a real merchant problem - from backend APIs to user-facing features
• Write clean, testable, well-documented code and take part in code reviews from day one
• Work in weekly sprint cycles, demoing progress every Friday and iterating fast
• Grow your skills in Kotlin and TypeScript through a hands-on bootcamp in week one, then apply them immediately
• Present your team's solution on Demo Day to senior engineers and stakeholders across SumUp

You might be a great fit if you…

• Are a final-year student or recent graduate in Computer Science, Software Engineering, or a related field
• Have built at least one full-stack application - through studies, a personal project, or freelance work
• Are familiar with Git and collaborative workflows such as branching, pull requests, and code review
• Have hands-on experience with at least one modern language - Java, Kotlin, Go, Python TypeScript preferred
• Are curious, self-driven, and learn fast - personal projects, open-source contributions, or online courses are a great signal
• Are fluent in English, as all programme communication is conducted in English

Why join SumUp?

• Impact with Purpose - Ship products used by millions of small businesses while building next-gen AI tools. This isn't a sandbox. 
• Come As You Are - A workplace that celebrates diversity and fosters an inclusion-first culture.
• Office Perks - Complimentary lunch every Thursday.
• Team Culture - Regular social events to connect and unwind. 

About SumUp

Be empowered to build things that matter. 

At SumUp, we're on a mission to empower small businesses across the globe by providing simple and affordable tools that allow them to thrive. Today, over 4 million businesses in 37 markets rely on SumUp as their financial partner to manage payments, finance and customer relationships. 

Our commitment to small businesses is reflected in our diverse team of over 3,000 SumUppers from over 90 nationalities, united by global collaboration and an innovative mindset. Our core values and culture shape everything we do, fostering inclusion, learning and belonging.

SumUp is proud to be an Equal Employment Opportunity employer, committed to building a safe, respectful, and diverse workplace where everyone can thrive. 

Discover more about our culture and opportunities on our careers website, and follow our journey on LinkedIn, and Instagram.