Find a job 
Featured Companies 
Featured Universities 
For Companies At a Glance
- Tasks: Design and develop secure payment solutions using C# and mentor junior engineers.
- Company: Join NMI, a leader in innovative payment gateway solutions.
- Benefits: Enjoy competitive salary, remote work, and generous holiday allowance.
- Why this job: Make an impact in the payments industry with cutting-edge technology.
- Qualifications: 5+ years in software development, strong C# skills, and mentoring experience.
- Other info: Flexible work culture with a focus on employee wellbeing and growth.
The predicted salary is between 41000 - 49000 ÂŁ per year.
Join to apply for the Senior Software Engineer (C#) role at NMI
Get AI-powered advice on this job and more exclusive features.
NMI is a leading provider of payment gateway solutions, specializing in card-present solutions and payment processing. Our innovative technologies empower businesses to securely accept payments and optimize transaction processes. With a focus on reliability, security, and innovation, we continuously push the boundaries of what\’s possible in the payments industry.
Ideal Candidate
- Backend development (C#/.NET)
- Mobile SDK development for Android (Java/Kotlin) or iOS (Objective-C/Swift)
The ideal candidate is a highly skilled software engineer with deep expertise in one or more of the following domains. You don’t need to be an expert in all these areas, but you should bring senior‑level technical depth and design experience in at least one, combined with the ability and curiosity to work across the stack when needed.
As a Senior Engineer, you will play a key role in designing, developing, and maintaining SDKs and backend components that enable secure, performant, and seamless payment transactions. You will be expected to take ownership of complex problems, influence architectural decisions, and contribute to improving our CI/CD, testing, and deployment processes. You’ll also provide mentorship, participate in design discussions, and help ensure that our systems and SDKs meet the highest standards of security, reliability, performance, and maintainability.
Key Responsibilities
- Design, develop, and maintain secure, scalable, high‑quality SDKs and backend services used in payment device integrations.
- Lead architectural and design discussions across backend and mobile platforms.
- Write and review well‑structured, maintainable, and efficient code.
- Collaborate closely with Product, QA, and Operations to ensure successful feature delivery.
- Mentor junior and mid‑level engineers, sharing best practices and guiding technical growth.
- Participate in the evolution of CI/CD pipelines and deployment automation.
- Ensure that all code and systems adhere to strong security and compliance requirements (e.g., PCI, OWASP).
- Investigate and resolve performance issues across SDKs and backend services.
- Contribute to cross‑team initiatives, including SDK standardization and shared libraries.
Skills & Experience
- Bachelor\’s degree in Computer Science, Information Technology, or equivalent experience.
- Minimum of 5 years of experience in developing complex software applications in a commercial environment.
- Advanced proficiency in C# (preferred) or Java, with a strong understanding of object‑oriented design principles and software architecture.
- Deep understanding of the Software Development Life Cycle (SDLC) and agile methodologies.
- Experience with relational databases (e.g., MySQL, SQL Server, Oracle) and optimizing database interactions.
- Strong knowledge of security best practices, including secure coding principles and compliance requirements (e.g., OWASP Top Ten, PCI, SOC2, HIPAA).
- Proficient in networking concepts such as sockets, HTTPS, DNS, and SSL.
- Deep knowledge of design patterns and their practical application.
- Proven ability to work independently while also fostering teamwork and cross‑team collaboration.
- Demonstrated ability to mentor junior engineers and contribute to the growth of the engineering team.
- Strong problem‑solving skills, with the ability to anticipate potential issues and proactively address them.
- Excellent communication skills, capable of explaining complex technical concepts to both technical and non‑technical stakeholders.
Benefits
- Annual bonus scheme dependent on individual and company performance.
- Annual salary of 48,000 – £60,000.
- 25 days holiday each year (+ bank holidays + 1 day after each year of service with up to a max. of 30 days).
- Workplace pension scheme.
- Private medical insurance (upon 30 days of employment).
- 7 hours per day, 35 hours per week.
- A remote first culture.
- Great work‑life balance with our Flexi‑time policy.
- Family Friendly policies (Enhanced Maternity and Paternity Pay and Shared Parental Leave).
- A chance to develop with an allocated company training budget.
- Bike2Work Scheme.
- Lifeworks, an Employee Assistance Programme which offers wellbeing, family and financial support services, such as assessments, resources and even 1:1 counselling sessions. It also offers interesting perks such as discounts on gyms, restaurants, high street retailers and cinema tickets.
- A strong commitment to employee wellbeing including mental health first aiders.
- Employee referral scheme with generous financial reward.
- Bonusly colleague reward scheme.
We’re looking for creative and passionate people who share our vision of making payments easy. If that sounds like you and you meet the requirements above, then please click on \’Apply for this job\’.
We are an Equal Opportunities employer and will provide reasonable support throughout the recruitment process to applicants who have a disability. Please let us know in advance so that any support, aids or adaptations can be put in place to assist you.
Please be aware that all offers of employment are made subject to receipt of satisfactory background and financial checks.
About Us
NMI enables our partners with choice, and challenges the one‑size‑fits‑all approach to payments. You\’ve probably used NMI in the last 24 hours without even realising it. We’re the platform that powers success for innovative tech created by SMBs, entrepreneurs and fintech start‑ups. We’re creative problem solvers who help visionaries smash through boundaries and think beyond what’s possible so they can think about what’s next. But we’re not just built for the tech savvy. We democratise the latest payments technology so that everyone can realise the benefits of easy payments across the full spectrum of commerce. We’re all about enabling more payments in more ways and more places.
Please note that in compliance with the data protection regulations within your jurisdiction, any personal information submitted with your job application may be collected and used by NMI for the purpose of recruitment and employment‑related activities. By submitting your application, you acknowledge and provide explicit consent to the processing of your personal information as described in our privacy policy found on our website. For more information on how we process your information, please read our privacy policy here: https://www.nmi.com/legal/privacy-policy/.
Salary Range, Depending On Experience
£48,000—£60,000 GBP
Seniority Level
Mid‑Senior level
Employment Type
Full‑time
Job Function
Engineering and Information Technology
#J-18808-Ljbffr
Senior Software Engineer (C#) employer: NMI
Contact Detail:
NMI Recruiting Team
StudySmarter Expert Advice 🤫
We think this is how you could land Senior Software Engineer (C#)
✨Tip Number 1
Network like a pro! Reach out to your connections in the industry, attend meetups, and engage in online forums. You never know who might have the inside scoop on job openings or can refer you directly.
✨Tip Number 2
Show off your skills! Create a portfolio showcasing your projects, especially those involving C# and payment solutions. This gives potential employers a taste of what you can do and sets you apart from the crowd.
✨Tip Number 3
Prepare for interviews by brushing up on common technical questions related to C# and software architecture. Practice coding challenges and be ready to discuss your past projects and how you tackled challenges.
✨Tip Number 4
Don’t forget to apply through our website! It’s the best way to ensure your application gets seen by the right people. Plus, it shows you’re genuinely interested in joining our team at NMI.
We think you need these skills to ace Senior Software Engineer (C#)
Some tips for your application 🫡
Tailor Your CV: Make sure your CV is tailored to the Senior Software Engineer role. Highlight your C# experience and any relevant projects that showcase your skills in payment processing or object-oriented programming. We want to see how you fit into our innovative team!
Showcase Your Projects: Include specific examples of projects you've worked on, especially those involving payment solutions or CI/CD pipelines. This gives us a clear picture of your hands-on experience and problem-solving abilities. Don't be shy—let your work shine!
Be Clear and Concise: When writing your application, keep it clear and to the point. Use bullet points for easy reading and make sure to communicate your technical skills effectively. We appreciate straightforward communication, especially when it comes to complex topics.
Apply Through Our Website: We encourage you to apply directly through our website. It’s the best way to ensure your application gets to the right people. Plus, it shows us you're serious about joining our team at NMI!
How to prepare for a job interview at NMI
✨Know Your C# Inside Out
Make sure you brush up on your C# skills before the interview. Be prepared to discuss object-oriented programming principles and how you've applied them in past projects. They’ll likely ask you to solve coding problems, so practice writing clean, efficient code.
✨Showcase Your Leadership Skills
As a Senior Software Engineer, you'll be expected to lead discussions and mentor junior engineers. Think of examples from your previous roles where you took charge of a project or helped others grow. This will demonstrate your ability to take ownership and foster collaboration.
✨Understand Payment Processing
Familiarise yourself with payment gateway solutions and the specific technologies used in card-present transactions. Knowing about PIN pads, card readers, and security best practices like PCI compliance will show that you're not just a coder but someone who understands the industry.
✨Prepare for Technical Discussions
Expect to engage in technical discussions about architecture and design patterns. Brush up on your knowledge of CI/CD pipelines and be ready to share your thoughts on improving automation processes. This will highlight your proactive approach to software development.
