Senior Developer

Job description

Senior Developer

Introduction

Addition partners with energy leaders to help bring in people who make technology work for real customers. This role sits at the centre of that mission—owning a key customer-facing platform and helping build new internal capability as the business modernises toward a more AI-enabled way of working.

Role Overview

• Location: Herfordshire, United Kingdom
• Package: £75,000
• Industry: Energy / Utilities (B2B)

What You’ll Be Doing:

• Take primary ownership of the B2B customer portal and its connected APIs and integrations
• Build and enhance RESTful back-end services and business logic using C# and ASP.NET
• Maintain and improve the integration layer across core systems, while keeping the platform stable and secure
• Support delivery through a sensible, agile SDLC—writing quality tests and collaborating closely with analysts and data owners
• Help shape the direction of the internal development function, including modernisation work and the adoption of AI tooling

Main Skills Needed

• Senior .NET delivery: Strong, hands-on experience with C# and .NET (Framework), delivering production-grade applications with real ownership
• API & service architecture: Confident building REST APIs and service-based architectures, with experience across UI and back-end (e.g., Razor Pages/MVC)
• Databases & integration: Solid Microsoft SQL Server skills (optimisation, stored procedures, schema design) and comfort working with legacy environments
• Azure & Linux hosting: Experience deploying applications in Microsoft Azure, including Linux-hosted environments and relevant Azure services
• Engineering best practice: Proficient with Git/GitHub (reviews, branching strategies) and working in agile teams using Jira/Confluence

What’s in It for You

• A competitive salary plus a strong benefits package, including enhanced pension, private medical insurance, and life insurance & income protection
• Career progression as the internal development function grows—plus genuine visibility with technical decision-making
• Extra touches that support day-to-day wellbeing: day off on your birthday, free parking, and fresh fruit/snacks/breakfast
• A culture built on collaboration and empowerment, with a real focus on continuous learning
• Profit share and social energy: amazing company parties and a community-focused office environment

Fancy a proper challenge? You might have just found it.

We are an equal opportunity employer and value diversity at our company. We do not discriminate on the basis of race, religion, colour, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status. By applying you are confirming you are happy to be added to the Addition Solutions mailing list regarding future suitable positions. You can opt out of this at any time simply by contacting one of our consultants.

Extra information

Status

Open

Education Level

Secondary School

Location

Hertfordshire

Type of Contract

Full-time jobs

Published at

01-07-2026

Full UK/EU driving license preferred

No

Car Preferred

No

Must be eligible to work in the EU

No

Cover Letter Required

No

Languages

English