Group S and delaware set a new standard for HR technology with Sienna

For Group S and delaware, Sienna represents far more than a traditional IT project. It is a strategic milestone in the ongoing modernization of HR technology.

Each month, Group S processes 270,000 payroll calculations for Belgian and international employers from 19 offices, supported by a team of more than 700 employees. From this frontline position, the HR service provider sees how rapidly the sector is evolving. HR organizations increasingly operate in an ecosystem where payroll, HR, ERP, CRM, finance, document flows and e-government systems are becoming ever more interconnected. At the same time, requirements around security, compliance, performance and usability continue to increase, while customers expect smooth, contextual and proactive support.

"The growing complexity of HR and payroll requires a fundamentally different way of working, as traditional payroll systems are often too rigid to adequately support today’s reality,” says Koen Van Loo, Chief IT & Digital Officer at Group S. “With Sienna, we are not merely building a new platform: we are transforming how HR services will be delivered in the years ahead. By further digitizing processes and embedding AI at the core, we help our people work more efficiently, reduce repetitive tasks and improve access to relevant information. This creates more room to support customers in a faster, more targeted way and to further enhance the quality of our services. This go-live is an important milestone for us and at the same time the starting point of a broader transformation.”

One platform, multiple processes

Sienna is the result of a close strategic collaboration between Group S and delaware. delaware guided Group S throughout the entire journey, from design and development to testing and go-live support.

The initial production release already consolidates several critical processes into a single digital environment, including employer and employee management, digital contract management, payroll finalization and post-payroll handling. Sienna is designed as a broad, extensible foundation for a future-proof HR landscape in which systems increasingly need to work together. As such, the platform also supports further integration with ERP, CRM, finance, document delivery and e-government environments.

Security considerations were embedded from day one, with features such as role-based access control, audit logging and multilingual support. Integrated reporting and dashboards provide employees with easy access to relevant operational and contextual insights.

Azure and EverESSt under the hood

Sienna is seamlessly integrated with EverESSt, widely regarded as one of the most powerful payroll engines on the market. Both systems exchange data in real time, eliminating double data entry and complex intermediate steps. While EverESSt hosts the payroll processing logic, Sienna offers employees an efficient and user-friendly interface to manage HR and payroll processes.

The solution was developed on Microsoft Azure as a secure, scalable and cloud-native environment, with a strong focus on performance, reliability and access management.

“AI has been part of this platform’s DNA from the very beginning. By leveraging GitHub Copilot and Microsoft Copilot, the teams were able to develop the platform faster and more effectively, improving code quality and collaboration,” says Stein Vermeulen, Regional Lead Cloud & AI at Microsoft Belgium. “Sienna demonstrates how an organization with a clear long-term vision approaches digital transformation: a cloud-native foundation with AI as an intelligent layer that gradually creates additional value. We are proud to support this journey together with Group S and delaware.”

Ready for future growth

In the coming months and years, Sienna will be rolled out and expanded in phases. The focus will be on scalability, efficiency, deeper integrations and enhanced support for both employees and customers. Over time, the platform is expected to help Group S work more proactively, further improve data quality and offer contextual support to employees in their day-to-day activities.

As an open platform, Sienna will also be able to integrate seamlessly with other HR and payroll tools in the future. Group S and delaware will bring Sienna to market as a white-label solution, enabling other HR organizations to integrate the platform into their own digital ecosystems.

“The sector is evolving rapidly and more than ever requires future-ready technology. Sienna was therefore developed as a lever for innovation, not only for Group S, but for the entire HR services landscape,” concludes Juan Staes, Partner at delaware. “This is not an IT replacement project, but a shared ambition to structurally modernize HR services. As a challenger, we want to help shape how the sector will develop in the years to come, together with Group S.”