Job Vacancy C# Software Engineer

Reading

CGI

Job position C# Software Engineer

Permanent

As soon as possible

Reading, England, United Kingdom

Published on 27/01/2026

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At CGI, you’ll play a pivotal role in building and sustaining secure, high-impact applications that underpin critical services for our clients. As a C# Developer, you’ll contribute to the full application lifecycle, combining hands-on development with 4th line support to ensure resilient, high-performing systems. Working within a collaborative, ownership-driven culture, you’ll help deliver measurable outcomes, strengthen long-term client relationships, and shape solutions that make a real difference in a highly secure environment.

CGI was recognised in the Sunday Times Best Places to Work List 2025 and has been named a UK ‘Best Employer’ by the Financial Times. We offer a competitive salary, excellent pension, private healthcare, plus a share scheme (3.5% + 3.5% matching) which makes you a CGI Partner not just an employee. We are committed to inclusivity, building a genuinely diverse community of tech talent and inspiring everyone to pursue careers in our sector, including our Armed Forces, and are proud to hold a Gold Award in recognition of our support of the Armed Forces Corporate Covenant. Join us and you’ll be part of an open, friendly community of experts. We’ll train and support you in taking your career wherever you want it to go.

Due to the secure nature of the programme, you will need to hold UK Security Clearance or be eligible to go through this clearance. This is a full-time onsite position based in our Reading office, five days per week. UK sole nationality is required.

Candidate profile

In this role, you will develop, maintain, and support a secure application using C#, ASP.NET, and SQL Server, taking ownership of both new functionality and the stability of a mature system. You’ll work closely with colleagues and, where appropriate, directly with the client, building trust through clear technical communication and reliable delivery. Supported by experienced peers, you’ll grow into a trusted technical authority and subject matter expert for the customer environment.

You will contribute to continuous improvement by applying strong software development practices, diagnosing complex issues, and ensuring solutions meet the highest security and quality standards.

Key responsibilities include:

- Develop & enhance secure applications using C# and ASP.NET

- Support & resolve complex 4th line application issues

- Analyse, debug, and improve mature production systems

- Manage code and work items using Azure DevOps

- Collaborate with stakeholders and communicate technical solutions clearly

- Contribute to best practice within a highly secure delivery environment

Required qualifications to be successful in this role

You will bring solid experience in Microsoft-based application development, with the ability to support and enhance secure, business-critical systems. You should be comfortable working with established codebases, applying strong debugging skills, and communicating effectively with both technical and non-technical stakeholders.

Essential qualifications:

- Strong experience with C# and ASP.NET

- Proven experience using SQL Server

- Familiarity with the Microsoft development toolchain

- Good understanding of modern software development practices

- Experience supporting and debugging mature applications

- Ability to work effectively in a secure environment

- Clear and confident technical communication skills

#LI-SB2

Working environment

Together, as owners, let’s turn meaningful insights into action.

Life at CGI is rooted in ownership, teamwork, respect and belonging. Here, you’ll reach your full potential because…

You are invited to be an owner from day 1 as we work together to bring our Dream to life. That’s why we call ourselves CGI Partners rather than employees. We benefit from our collective success and actively shape our company’s strategy and direction.

Your work creates value. You’ll develop innovative solutions and build relationships with teammates and clients while accessing global capabilities to scale your ideas, embrace new opportunities, and benefit from expansive industry and technology expertise.

You’ll shape your career by joining a company built to grow and last. You’ll be supported by leaders who care about your health and well-being and provide you with opportunities to deepen your skills and broaden your horizons.

Come join our team—one of the largest IT and business consulting services firms in the world.

Discover CGI

London, England, United Kingdom

> 1000 employees

IT services

We are a global business with 91,500 professionals across hundreds of locations worldwide, providing end-to-end IT and business process services that drive our clients’ businesses. In the UK alone, we have around 6,000 member-partners working across 19 towns and cities, doing everything from writing complex code to designing sophisticated software solutions. The work we do powers some of the most ambitious projects that touch the lives of many. Our approach sets us apart, characterised by our proximity model, international presence, expertise, and operational excellence. We organise our operations within metro markets where our clients have concentrated footprints, empowering our local teams to build trusted, in-person relationships. As you build your career here, you’ll develop your skills, share your insights, and work side-by-side with colleagues and clients on innovative solutions that address the most complex issues. Our commitment to ownership, flexibility, and being approachable makes us easy to do business with. Join us, and together, as owners, let’s turn meaningful insights into action to meet the needs and balance the interests of our clients, shareholders, communities, and each other. Benefits: - Insurance coverage - Medical benefits - Pension plan - Member Assistant Programme - Check4Cancer - Flexible time off - Share Purchase Plan - Member discounts - Dental benefits - Vision benefits - Profit Participation Plan - Health and Wellbeing Programme

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C# Software Engineer

CGI