Full Stack .NET Engineer

Job Title: Full Stack .NET Engineer
Location: Belfast, Northern Ireland
Work Arrangement: Hybrid
Position Overview: We are seeking experienced AI-enabled .NET full-stack engineers who can quickly understand our existing codebase and significantly contribute to the development of complex, innovative solutions in our fast-paced fintech environment. As a key member of our engineering team, you will take ownership of significant features, driving them from conception to deployment. We need a versatile 'Swiss Army Knife'—a engineer who is comfortable across the entire SDLC, from architectural design and implementation to testing and deployment. Your experience and expertise will be vital in delivering high-quality, robust solutions. Join our growing team and make a substantial impact on our platform! 

We are an AI-enabled engineering team, and we believe the future is about empowering engineers with the latest tools, building through custom skills, agents, and harnesses, and we are looking for people who embrace AI, are excited about the future, and want to help shape the way we embed AI tooling throughout our developer experience.

Primary Job Responsibilities:

• Design & build future-proof solutions to support growing business needs while thoroughly considering the system impact
• Work closely with our senior engineers to develop solutions from idea to implementation by estimating, planning, tracking and managing progress, risks, and dependencies.
• Gather and refine requirements, and release software in a timely fashion
• Be adaptive and strike a good balance between speed and efficiency
• Work with our technical support team to identify, reproduce, and remediate bug tickets
• Build and deliver features through agentic tooling — designing, iterating on, and improving our custom skills, agents, and harnesses as part of the work
• Contribute prompts, skills, and workflow improvements back to the team so our AI-enabled developer experience compounds
• Perform other duties required by Management

Essential Criteria:

• BSc or MSc in Computer Science / related qualification OR commercial experience of developing in C#, Java or other OO programming languages
• Minimum 2 years of hands-on commercial experience programming on the .NET platform using C#, including ASP.NET (MVC)
• Experience with Design Patterns, refactoring, OO Design and related areas
• Practical hands-on experience with AI coding assistants and agentic engineering workflows, and a genuine appetite to work primarily through agents — owning architecture, review, and quality rather than typing every line
• Exposure to building web services using Web API
• An understanding of database design and development
• Hands-on experience with HTML, JavaScript, CSS including jQuery
• Strong attention to detail and work ethic
• Strong analytical and problem-solving skills
• Excellent communication (both written and verbal) and interpersonal skills
• Experience of cloud technologies such as Azure/AWS/GCP
• Previous experience working with source control tools (TFS, SVN, or GIT)
• Legal right to work in the UK

Desirable Criteria:

• Experience with Azure Functions and Queues
• Experience building custom agent skills, harnesses, MCP servers, or prompt libraries
• Experience defining evals, guardrails, or review practices for AI-generated code
• Experience in testing methodologies
• Experience of LEAN software development practices
• Knowledge of CI/CD systems and implementation practices
• Hands-on experience with front-end frameworks such as Bootstrap
• Knowledge on .NET Core and Entity framework Code First migrations
• Proficient with Claude or Claude Code
• Experience in Financial services industry

What We Offer:

• Private health insurance
• Group life death benefit
• Auto-enrollment pension with employer contributions matched to 5%
• 25 days holiday per year
• 10 statutory/bank holidays per year
• Opportunities for professional growth and development
• A collaborative and innovative work environment

About Us: Biller Genie is an award-winning B2B SaaS platform, recently ranked #516 on the Inc. 5000 list of the fastest-growing companies in the United States. With headquarters in Orlando and a growing Engineering Hub in Belfast, we're scaling fast, with over 100 hires planned through 2028.
Our Mission: To provide an automated A/R platform that seamlessly integrates existing business processes for the SMB market.
Our Core Values:
Get S**t Done Right - We work hard and ensure tasks are completed correctly and on time, every time.
Own it - We are subject matter experts who know what we know, and we are confident enough to speak up when we see something wrong.
Catch Up - We are high performers and love a fast-paced environment.
Believe in the Genie - We are passionate about where we are going as a team, and we show we care.
Class Shines - We are articulate professionals who carry ourselves well and speak with purpose.

How We Work: Our engineers work with agents and harnesses as a default, not an experiment. Our interview process includes a practical exercise using AI tooling. If that sounds like the way you want to build, you will thrive here; if you would rather write every line by hand, this is likely not the right fit. 
Biller Genie is an equal opportunities employer. We welcome applications from all suitably qualified persons. 

Please note we are unable to offer visa sponsorship.