The UK is home to a strong selection of top companies specialising in .NET development. These agencies create custom applications, enterprise platforms and cloud-ready systems built on Microsoft’s framework to support businesses across many sectors.
They work with organisations of all sizes, from growing startups to established enterprises, delivering reliable web applications, desktop tools and integrated solutions that fit existing technology environments. Their focus stays on clean code, performance and long-term maintainability using current .NET tools and practices.
1. Itexus
Itexus focuses on supplying senior .NET developers experienced in current frameworks, cloud platforms and related practices for application work. Our work follows clear engineering standards that include clean code, automated testing and structured delivery methods so projects stay consistent from start to finish. We structure cooperation to keep all code and data under client control with signed agreements in place.
Our approach takes into account the specific needs of businesses in the UK and includes providing .NET development services there. We support flexible resource adjustments and knowledge transfer so the work integrates smoothly with existing processes. Continuous attention goes to security practices, performance checks and ongoing maintenance after the main build phase ends.
Key Highlights:
- Clean and maintainable code practices
- Secure development and infrastructure processes
- Flexible resource scaling options
- AI-assisted delivery methods
- Structured knowledge transfer focus
Services:
- .NET development
- Senior developer hiring
- Custom application building
- Cloud-based solution work
- Application modernisation
- Microservices architecture support
Contact Information:
- Website: itexus.com
- Email: [email protected]
- Address: 8, The Green, STE road, Dover, DE 19901, United States
- LinkedIn: www.linkedin.com/company/itexus
- Facebook: www.facebook.com/itexus
- Twitter: x.com/ItexusSoft
- Instagram: www.instagram.com/itexus.soft
2. I-Finity
I-Finity delivers specialist .NET development for bespoke web solutions designed to match specific requirements. The company creates custom applications that operate across platforms, browsers and devices. They also build and host solutions on Azure using Umbraco CMS, which runs on the .NET framework.
The agency focuses on cloud-based .NET applications, often structured as Software-as-a-Service products that support business growth. I-Finity modernises outdated .NET applications through upgrades that improve scalability, resilience and performance with minimal downtime. They handle migration of existing .NET applications to Azure while reviewing options for better security. The company supplies ongoing maintenance and support that covers performance optimisation, security updates and backup services. Their work draws on experience across Microsoft products to produce integrated applications that remain reliable over time.
Key Highlights:
- Microsoft Partner accreditation
- Custom web solution focus
- Azure and Umbraco integration capability
- Long-term maintenance options
Services:
- Custom application development
- CMS development with Umbraco
- Cloud-based SaaS product creation
- Application modernisation
- Migration to Azure
- Ongoing maintenance and support
Contact Information:
- Website: www.i-finity.co.uk
- Phone: 01904 652100
- Email: [email protected]
- Address: Blake House, 66 Bootham, York, YO30 7BZ
- LinkedIn: www.linkedin.com/company/i-finity
- Facebook: www.facebook.com/IFinityHQ
- Twitter: x.com/ifinityhq
- Instagram: www.instagram.com/ifinityhq
3. AssemblySoft
AssemblySoft operates as a .NET development company that builds full-stack applications for web, mobile and cloud environments. The company creates solutions ranging from Azure microservices and Blazor web apps to Windows desktop and .NET MAUI mobile projects. They deliver custom software that covers end-to-end needs from initial builds to ongoing delivery.
The agency specialises in integration work that connects applications with databases, APIs, ERPs and CRMs. AssemblySoft handles migration and modernisation of legacy systems to current .NET versions with an emphasis on uninterrupted operation. They produce cloud-native solutions that use microservices architecture and support deployment on Azure as well as other platforms. The company also develops e-commerce back-ends with secure payment handling and builds enterprise platforms such as ERP, CRM and business intelligence tools. Their developers apply tools from the broader Microsoft ecosystem to keep projects aligned with practical business requirements.
Key Highlights:
- Microsoft Partner status
- Full-stack coverage across platforms
- Focus on cloud-native delivery
- In-house UK managed team
Services:
- Custom software development
- Integration and API development
- Migration and modernisation
- Cloud-based solution building
- E-commerce platform work
Contact Information:
- Website: www.assemblysoft.com
- Phone: +441202428719
- Email: [email protected]
- Address: 2 Woodland Walk, Bournemouth, Dorset BH5 1LU, United Kingdom
- LinkedIn: www.linkedin.com/company/Assemblysoft
4. Intelivita
Intelivita supplies .NET development that covers custom applications, web platforms and mobile solutions. The company builds secure software tailored to individual business processes and data needs. They produce ASP.NET web applications that remain dynamic and scalable.
The agency develops cross-platform mobile applications using the relevant .NET frameworks. Intelivita creates content management systems based on ASP.NET Core or related platforms. They also design multi-tenant cloud applications structured as Software-as-a-Service products. The company modernises existing systems by moving them from older framework versions to current ones. Their approach includes planning, integration, deployment and continued maintenance so that applications stay aligned with operational goals over time.
Key Highlights:
- Experience across web and mobile platforms
- End-to-end lifecycle coverage
- Focus on business-aligned solutions
- Support for cloud-ready designs
- Integration with Microsoft ecosystem tools
Services:
- Custom application development
- ASP.NET web development
- Mobile app development
- CMS development
- SaaS product creation
- Application modernisation
Contact Information:
- Website: www.intelivita.co.uk
- Phone: +44 161 504 3600
- Email: [email protected]
- Address: Kemp House, 152-160 City Rd, London, EC1V 2NX, UK
- LinkedIn: www.linkedin.com/company/intelivita
- Facebook: www.facebook.com/intelivita
- Twitter: x.com/Intelivita
- Instagram: www.instagram.com/intelivita
5. Blacklight Software
Blacklight Software builds bespoke systems entirely on the .NET stack for UK clients. The company produces line-of-business applications shaped around existing workflows rather than forcing changes into standard products. They create customer and client portals that support self-service access.
The agency develops internal tools and mobile apps that replace paper forms and spreadsheets. Blacklight Software handles integrations that connect systems such as SAP, Oracle and payment platforms so data moves without manual re-entry. They also replace legacy systems through gradual modernisation that keeps operations running. All work stays in-house with the same team handling scoping, coding and post-launch support. The company has maintained Microsoft Partner status and uses the framework for applications that run on Windows, Linux or Mac, either on-premise or in the cloud.
Key Highlights:
- In-house UK development team
- Microsoft Partner accreditation
- Long-term post-launch support
- Focus on workflow-specific systems
Services:
- Line-of-business system building
- Customer and client portal creation
- Internal tools and mobile app development
- System integration work
- Legacy replacement and modernisation
Contact Information:
- Website: www.blacklightsoftware.com
- Phone: +44 1924 640350
- Email: [email protected]
- Address: 4 South Park Way, Junction 41 Business Park, Wakefield, WF2 0XJ
- LinkedIn: www.linkedin.com/company/blacklight-software
- Twitter: x.com/BlackLightUK
6. Software Planet Group
Software Planet Group provides .NET development that spans design, implementation, testing, integration and modernisation of applications. The company creates tailored solutions that address specific client requirements across a range of project types. They offer consulting that helps shape technical direction and architecture.
The agency modernises legacy codebases and develops desktop applications. Software Planet Group supports migration of applications to the cloud and builds the underlying architecture for new projects. They also supply CTO and tech lead assistance where needed. The company covers the full lifecycle so that solutions receive ongoing refinement and maintenance after launch. Their work stays focused on producing secure applications that fit the practical needs of each organisation without unnecessary complexity.
Key Highlights:
- Full lifecycle coverage
- Consulting and architecture support
- Focus on tailored solutions
- Post-deployment maintenance options
- Transparent communication approach
Services:
- Bespoke development
- Consulting services
- Legacy codebase modernisation
- Desktop app development
- Application migration to the cloud
- Architecture building
Contact Information:
- Website: softwareplanetgroup.co.uk
- Phone: +441483802423
- Email: [email protected]
- Address: Austen house, 1 Station View, Guildford GU1 4AR, UK
- LinkedIn: www.linkedin.com/company/software-planet-group
- Facebook: www.facebook.com/softwareplanetgroup
7. Spinbox
Spinbox delivers .NET development that turns software architecture into practical digital solutions. The company builds dynamic websites, APIs and enterprise applications using the framework. They create custom applications that fit unique business requirements whether starting from scratch or improving existing systems.
The agency works with a range of related technologies including ASP.NET, Core, MVC and Blazor. Spinbox applies agile methods that allow projects to adapt through rapid prototyping and continuous testing. They focus on solutions that improve system efficiency and support seamless integration with current infrastructure. The company includes consultants and project managers alongside developers so that delivery stays aligned with strategic goals. Their process covers design through to testing so finished applications arrive ready for use.
Key Highlights:
- Decades of hands-on framework experience
- Full service from design to testing
- Agile project approach
- Focus on business process integration
Services:
- Custom application development
- Website and API building
- Enterprise application work
- Existing system enhancement
- Integration with current infrastructure
Contact Information:
- Website: www.spinbox.co.uk
- Phone: +44 (0)1908 592595
- Address: 5 & 6 Walker Avenue Milton Keynes MK12 5TW United Kingdom
- LinkedIn: www.linkedin.com/company/spinbox-digital
- Facebook: www.facebook.com/Spinbox-266542391203
- Twitter: x.com/SpinboxDigital
8. TatvaSoft
TatvaSoft develops sophisticated multifunctional websites and applications using .NET frameworks that support business processes. The company creates custom software applications across ASP.NET, .NET Core, VB.NET, MVC, C sharp, MVVM, entity framework and Xamarin. They handle Microsoft Azure development for cloud-native applications that incorporate Azure apps, Blob, Stream Analytics and SQL databases.
The agency produces ASP.NET web applications with C sharp and VB.NET that remain functionally rich and secure. TatvaSoft builds universal apps featuring interactive interfaces and asynchronous systems that share a common API surface. They manage full-cycle .NET Core development covering design, analysis, testing, integration and deployment. The company develops WPF applications for standalone tools, XAML-based work, custom control libraries and class libraries. They also supply Xamarin development for cross-platform iOS and Android applications along with ongoing management of legacy apps and enterprise application integration that links multiple systems in real time.
Key Highlights:
- Microsoft certified status
- Full-cycle development coverage
- Cloud-native application focus
- Cross-platform mobile capability
- Dedicated team options
Services:
- Azure development
- ASP.NET web development
- Universal app development
- Core framework work
- WPF application development
- Xamarin development
- Application management and integration
Contact Information:
- Website: www.tatvasoft.com
- Phone: +44 742 409 8452
- Email: [email protected]
- Address: 307, Euston Road, London NW1 3AD, United Kingdom
- LinkedIn: www.linkedin.com/company/tatvasoft
- Facebook: www.facebook.com/TatvaSoft
- Twitter: x.com/tatvasoft
9. Audacia
Audacia builds large-scale complex applications using the latest versions of .NET for organisations that require mission-critical platforms. The company creates secure high-performance web apps and services with ASP.NET and Blazor that run on Windows, Linux and the cloud. They develop intuitive native mobile apps for iOS, Android and Windows from a single codebase using Xamarin or MAUI.
The agency produces scalable and resilient APIs and microservices with ASP.NET Core and Kubernetes. Audacia leverages .NET with Azure to deliver enterprise-grade cloud-native apps that use serverless resources, containers and PaaS options. They create custom machine learning models with ML.NET that integrate AI into applications for improved services and data analytics. The company also supplies development experts for team augmentation so internal groups can complete projects with added capacity. Their work follows established practices for resilience, speed and longevity across different application architectures.
Key Highlights:
- Microsoft Gold certified status
- Focus on mission-critical platforms
- Cloud-native delivery capability
Services:
- Web application building
- Mobile application development
- API and microservices creation
- Cloud-native app development
- Machine learning model work
- Team augmentation
Contact Information:
- Website: audacia.co.uk
- Phone: 0113 543 1300
- Email: [email protected]
- Address: 46 The Calls, Leeds, West Yorkshire, UK, LS2 7EY
- LinkedIn: www.linkedin.com/company/audacia-consulting
- Facebook: www.facebook.com/AudaciaTechnology
- Twitter: x.com/audacia_tech
10. Innovensa
Innovensa provides custom .NET development for UK businesses that need secure and scalable web applications. The company builds solutions with Blazor, ASP.NET Core, Azure and SQL Server. They engineer custom ASP.NET web applications that support complex internal management systems and high-traffic customer portals.
The agency specialises in rich interactive user interfaces using Blazor so the full application stays in a single C sharp codebase. Innovensa develops cloud-native solutions designed for Microsoft Azure that remain scalable and cost-efficient. They create secure APIs that connect CRM, accounting and other platforms to automate workflows and remove duplicate data entry. The company also supplies specialist support and proactive maintenance that protects long-term security and performance. They modernise legacy systems including older MS Access databases and classic ASP or VB.NET applications by migrating or rebuilding them into current .NET web applications.
Key Highlights:
- Microsoft Partner status
- Hertfordshire-based team
- Focus on legacy modernisation
- Long-term support options
Services:
- Custom ASP.NET web applications
- Blazor and front-end development
- Cloud-native Azure solutions
- API development and integration
- Support and maintenance
- Legacy system modernisation
Contact Information:
- Website: www.innovensa.co.uk
- Phone: 01707 538 035
- Email: [email protected]
- Address: HatTech Business Centre, Beaconsfield Rd, Hatfield, Hertfordshire, AL10 8FF
- LinkedIn: www.linkedin.com/company/innovensa
- Twitter: x.com/innovensa
11. GoodCore
GoodCore builds high-performance web and desktop applications using classic and modern technologies that include Windows Forms, WPF, MVC and Blazor frameworks. The company delivers custom enterprise solutions tailored to specific business needs. They produce web applications and desktop applications for Windows environments.
The agency handles modernisation of legacy apps and migration from older .NET versions to Core. GoodCore develops cross-platform mobile apps with Xamarin and creates .NET web APIs. They manage cloud deployment along with microservices development and deployment. The company also works on SignalR projects as well as Sitecore, Umbraco and Office365 integrations. Their teams cover projects at any stage and supply ongoing support so applications remain efficient after launch. Intellectual property rights stay with the client for every element produced.
Key Highlights:
- Experience across web and desktop
- Focus on custom enterprise work
- Legacy modernisation capability
- Cloud and microservices options
- IP protection for clients
- Multiple engagement models
Services:
- Custom enterprise solutions
- Web application development
- Desktop application building
- Legacy app modernisation
- Core framework migration
- Cross-platform mobile development
Contact Information:
- Website: www.goodcore.co.uk
- Phone: 020 8781 6903
- Email: [email protected]
- Address: Airport House, Purley Way, Croydon CR0 0XZ
- LinkedIn: www.linkedin.com/company/goodcore-software
- Facebook: www.facebook.com/goodcoresoftware
12. Pulsion
Pulsion delivers scalable and secure applications through .NET development services that automate business processes. The company creates custom software solutions that remain unique and interactive. They produce web applications with responsive designs using current .NET technologies.
The agency develops mobile applications that integrate .NET with MAUI or implement the framework alongside Xamarin and Blazor Hybrid for native apps from a single codebase. Pulsion builds desktop apps using Windows Forms for event-driven programming or WPF for data-binding with the MVVM pattern. They handle migration of legacy applications to current frameworks and create cross-platform applications that run on multiple devices. The company develops APIs that connect to ERP systems, project management tools and CRM platforms. They also supply e-commerce back-ends with payment gateway integration, enterprise applications with bespoke ERP and CRM tools, and cloud-based solutions that use microservices along with Docker and Kubernetes.
Key Highlights:
- Long-standing development experience
- Focus on custom and web solutions
- Cross-platform mobile capability
Services:
- Custom software development
- Web application building
- Mobile development
- Desktop app creation
- Migration and modernisation
- Cross-platform application work
- API development and integration
Contact Information:
- Website: www.pulsion.co.uk
- Phone: 441413522280
- Email: [email protected]
- Address: 5 Eagle Street, Craighall Business Park, Glasgow, G4 9XA
- LinkedIn: www.linkedin.com/company/pulsion-technology
13. Whiz Solutions
Whiz Solutions offers full ASP.NET development solutions for organisations that need to create, update or scale applications. The company handles processes from consultation and architecture design through to deployment and optimisation. They produce custom ASP.NET websites built for efficiency, security and scalability.
The agency develops ASP.NET Core applications that run across platforms with strong performance. Whiz Solutions builds enterprise software that automates business operations. They create secure APIs that connect payment gateways, CRMs, ERPs and cloud infrastructure. The company produces cloud-based applications using Microsoft Azure. They modernise legacy .NET applications and handle migration of existing systems or databases to current ASP.NET technology. Ongoing maintenance covers bug fixing, security updates and performance tuning so applications stay current.
Key Highlights:
- Full process coverage from consultation to optimisation
- Focus on custom and Core applications
- Enterprise software capability
- Cloud and migration options
Services:
- Custom web development
- Core application building
- Enterprise software creation
- API development
- Cloud application work
- Legacy modernisation
- Migration services
- Maintenance and technical support
Contact Information:
- Website: www.whizsolutions.co.uk
- Phone: +44 (0) 742 715 4931
- Email: [email protected]
- Address: Suite 32, Winsor & Newton Building, Whitefriars Avenue, Harrow, England, HA3 5RN, United Kingdom
- LinkedIn: www.linkedin.com/company/whiz-solutions-ltd
- Facebook: www.facebook.com/whizsolutionsltd
- Twitter: x.com/whizsolutionsUK
14. Chilliapple
Chilliapple builds .NET software development solutions for businesses and enterprises. The company specialises in tailored websites and applications using Microsoft’s framework. They create custom applications with functionality that supports growth and operations.
The agency develops applications for both web and mobile platforms that deliver seamless experiences across devices. Chilliapple produces Software-as-a-Service platforms that scale with user bases, covering architecture through to deployment and updates. They modernise legacy applications after technical assessment to improve scalability, speed and resilience. The company builds enterprise-grade applications including modules for finance, HR, supply chain and CRM. Maintenance packages include regular updates, system health checks, performance optimisation and security enhancements so applications remain fast and secure.
Key Highlights:
- Focus on tailored websites and applications
- Web and mobile platform coverage
- SaaS platform capability
- Enterprise module experience
- Ongoing maintenance packages
Services:
- Custom application development
- Web and mobile app building
- SaaS platform creation
- Application modernisation
- Enterprise app development
- Maintenance and support
Contact Information:
- Website: www.chilliapple.co.uk
- Phone: 01732753101
- Email: [email protected]
- Address: 16 Upper Woburn Place, London WC1H 0AF, United Kingdom
- LinkedIn: www.linkedin.com/company/chilliapple-ltd
- Facebook: www.facebook.com/ChilliappleLimited
- Twitter: x.com/chilliapple
- Instagram: www.instagram.com/chilliappleltd
15. Hidden Brains
Hidden Brains supplies ASP.NET development services for building feature-rich web solutions. The company creates custom ASP.NET solutions tailored to specific needs. They develop desktop applications that leverage Windows GUI support.
The agency produces mobile applications using current techniques that match ongoing requirements. Hidden Brains handles custom development after market research so solutions fit business needs. They integrate applications with cloud services such as Amazon Web Services and Microsoft Azure. The company provides maintenance and support to keep applications running without performance or security issues. They also manage seamless migration of existing web apps from other platforms to .NET with no data loss. Work covers a range of application types so projects stay aligned with practical operational demands.
Key Highlights:
- Custom solution focus
- Desktop and mobile coverage
- Cloud integration capability
- Migration support
Services:
- Desktop app development
- Mobile app development
- Custom development
- Cloud integration
- Maintenance and support
- Migration services
Contact Information:
- Website: www.hiddenbrains.co.uk
- Phone: +44 (0)20-7993-2188
- Email: [email protected]
- Address: Unit P Hunting Gate, East Portway, Andover, Hampshire, SP10 3ER, UK
- LinkedIn: www.linkedin.com/company/hiddenbrains-infotech
- Facebook: www.facebook.com/HiddenBrains
- Twitter: x.com/HiddenBrains
16. DevsTree
DevsTree delivers ASP.NET web development solutions designed for security, scalability and performance. The company builds web applications, APIs and enterprise systems. They work with MVC, Core frameworks, cloud integration and database-driven architectures.
The agency produces custom ASP.NET web applications that remain reliable and maintainable. DevsTree handles Core development along with enterprise application work. They create MVC applications and develop APIs with backend components. The company also manages application migration and modernisation so existing systems move to current structures. Their approach follows architecture standards and deployment practices that keep solutions aligned with business goals over time. Work stays focused on data-driven systems that support operational needs without unnecessary complexity.
Key Highlights:
- Enterprise-grade application focus
- MVC and Core framework coverage
- Cloud integration capability
- Migration and modernisation options
Services:
- Custom web application development
- Core development
- Enterprise application building
- MVC application work
- API and backend development
- Application migration and modernisation
Contact Information:
- Website: www.devstree.co.uk
- Phone: +44 7404 650992
- Email: [email protected]
- Address: Rotunda Point, 11 Hartfield Cres, London SW19 3RL, United Kingdom
- LinkedIn: www.linkedin.com/company/devstreeuk
- Facebook: www.facebook.com/devstreeitsolutionsuk
- Twitter: x.com/DevstreeUK
- Instagram: www.instagram.com/devstree.uk
17. A-listware
A-listware creates user-friendly web-based products that deliver value. The company offers comprehensive web development services using current technologies including Microsoft .NET. They handle projects such as customer-facing web applications, internal management portals and e-commerce stores.
The agency builds web portals that automatically collect data from corporate systems for up-to-date information. A-listware produces websites with user-friendly page editors for managing dynamic content. They develop e-commerce solutions that range from entry-level shops to custom setups for larger businesses, with a focus on automation. The company also creates web applications that manage professional activities and integrate corporate tools. Their process covers business analysis, design, architecture, front-end and back-end work, integration, testing and continuous support so products remain functional after launch.
Key Highlights:
- Focus on web-based products
- Portal and website capability
- E-commerce solution experience
- Continuous support options
Services:
- Web portal creation
- Website development
- E-commerce solution building
- Web application development
- Integration work
- Continuous support and evolution
Contact Information:
- Website: a-listware.com
- Phone: +44 (0)142 439 01 40
- Email: [email protected]
- Address: St. Leonards-On-Sea, TN37 7TA, UK
- LinkedIn: www.linkedin.com/company/a-listware
- Facebook: www.facebook.com/alistware
Conclusion
Finding the right fit among .NET development companies in the UK comes down to practical match rather than any single standout trait. Some lean harder into custom application work, others into modernising older systems or handling cloud moves – and that variety is useful once you know exactly what the project demands. Most of the credible options keep things grounded: clear scopes, steady delivery, and support that doesn’t vanish after launch. It still takes a bit of homework to line up the technical side with your actual workflows, but the market is mature enough that solid choices exist without chasing every new framework trend.