From On-Premise to Cloud: How RET Migrated 3,500+ Payrolls Without Anyone Noticing

When you're processing payroll for over 3,500 employees who keep an entire city moving, there's no room for error. Here's how RET pulled off a complex cloud migration without missing a single payment.

RET is a household name for commuters in the Rotterdam metropolitan region. Every day, more than 550,000 people rely on their buses, metros, and trams to get where they need to go. Behind the scenes, this means not just keeping transport running on schedule, but also ensuring more than 3,500 employees get paid accurately and on time, every month.

So when RET decided to migrate their payroll system to the cloud, the stakes were high. The transition had to be seamless—no disruptions, no delays, no mistakes.

Julia Wybenga, project manager at RET, led the migration from their on-premise system to SAP SuccessFactors Employee Central Payroll. She shares how they completed this major project on schedule.

"SD Worx gave us a clear timeline estimate at the start, and they actually stuck to it. I'm not used to that—usually these kinds of projects overrun." 

The migration came with its own unique challenges. RET was facing a tight deadline due to upcoming collective labor agreement (CLA) changes that couldn't be delayed. At the same time, their payroll team was stretched thin.

"Several colleagues from the payroll team retired, and they took a wealth of knowledge with them," Julia explains. "Bringing in external support became essential, which added another layer of complexity—we had to ensure the new system and processes would be properly embedded in the organization for the long term."

The team knew that future payroll employees would need to work confidently with the new system, so they developed comprehensive work instructions to safeguard the process and institutional knowledge. 

Despite the challenges, the transition went remarkably smoothly. Julia credits SD Worx's structured approach: Cloud Jump, a phased methodology that breaks down complex migrations into manageable steps.

"Cloud Jump provided clear guidance on what we were going to do and when. SD Worx gave us a crystal-clear picture of how long each phase would take, which is invaluable for planning and managing expectations internally."

Julia joined the project at the readiness check phase, a critical first step for migrations of this scale. "The readiness check clarified exactly what we would and wouldn't do in this project, and which areas needed extra attention. It also mapped out all the technical steps and architectural changes. This allowed us to make informed decisions and properly structure the phases that followed." 

When asked what made the project successful, Julia doesn't hesitate: "Clarity. A migration process requires absolute clarity—about what needs to be done, when, and by whom. Setting those expectations is crucial, and that demands good communication."

Sometimes that meant very intensive contact. "We had detailed plans for everything—testing schedules, freeze periods when certain components couldn't be used temporarily...at critical points, we even had daily calls. That kind of responsiveness allows you to act quickly and resolve issues before they become problems. It builds trust."

Julia has high praise for the SD Worx team: "The people at SD Worx really know their stuff. They're knowledgeable, helpful, and true problem-solvers. They're also highly accessible and open to extra contact when needed. That level of engagement kept the process on track, without disruptions or information loss."

For Julia, the real measure of success was simple: "Employees just want to receive their salaries on time. They shouldn't notice anything during a process like this. And we succeeded."

The payroll team members who would work with the new system received thorough training and knew exactly what to do. The rest of RET's staff were eventually informed that the migration had taken place, but otherwise? They didn't notice a thing.

"It was truly a seamless transition," Julia says. "Which is exactly what we aimed for."

Beyond the immediate success, the migration positions RET strategically for the future. Their payroll system and IT landscape are now fully compliant and ready to scale.

"This transition was complex because so many different systems were involved," Julia notes. "But with the move to SAP Cloud combined with Payroll Control Center, we've taken a major step toward future-proofing our systems. The scalability ensures the solution can grow alongside RET as our needs evolve."

The migration marks another milestone in a long-standing relationship. SD Worx will continue as the system administrator, providing support for system updates and further developments within SAP SuccessFactors Employee Central Payroll.

"Next, we'll be working on authorizations, process improvements, and integrations with SuccessFactors TIME and SAP S/4HANA," Julia explains. "The collaboration between RET and SD Worx continues—and I'm confident it will for years to come."

Images: Rick Keus, commissioned by RET