--- title: What I’ve learned about global mobility so far description: Three months into global mobility, Zak shares what surprised him most, from tax on the tax to a payroll that pays no one and rules that never stand still. image: https://www.certino.com/hubfs/what-ive-learned-about-global-mobility-cover.png --- [Skip to content](https://www.certino.com/blog/what-ive-learned-about-global-mobility-so-far#main-content) [![Certino Ltd. Logo](https://www.certino.com/hubfs/march-2021/globals/certino.svg)](https://www.certino.com/) ![](https://cdn2.hubspot.net/hubfs/234700/_nov_2019/globals/nav.svg) - [Home](https://www.certino.com) - [Platform](https://www.certino.com/platform) - [Managed service](https://www.certino.com/managed-service) - [About us](https://www.certino.com/about-us) - [Blog](https://www.certino.com/blog) - [Book a call](https://www.certino.com/book-a-consultation) [Blog](https://www.certino.com/blog)  /  [Global Mobility](https://www.certino.com/blog/tag/global-mobility) # What I’ve learned about global mobility so far ![](https://www.certino.com/hubfs/zak-haralambous.png) [Zak Haralambous](https://www.certino.com/blog/author/zak-haralambous) • 2 November 2026 • 3 min read ![Zak Haralambous smiling in a circular photo on a notebook-paper background, surrounded by five sticky notes: “Tax on the tax”, “A payroll that pays no one”, “The rules never stand still”, “Hard to explain in one sentence” and “The expertise behind it”, above the caption “What I’ve learned so far”.](https://www.certino.com/hubfs/what-ive-learned-about-global-mobility-cover.png) When I joined Certino, I assumed global mobility simply meant people working and moving around the world. That’s part of it, but I quickly learned how much sits behind every international move: where tax is due, how it’s calculated and how it’s reported. Three months in, I’m still learning every week. But a few things have stood out to me more than anything else, so I wanted to share them. ### 1. Tax on the tax One of the first things that caught my attention was the [tax gross-up](https://www.certino.com/blog/same-inputs-same-answer-why-cross-border-gross-ups-drift-and-how-to-stop-it). The idea of a company paying tax on the tax it has already covered for an employee was something I’d never come across before joining Certino. What stands out to me now is the level of precision it demands. It’s one of the clearest examples of how carefully every calculation in this area needs to be worked through, and how a change in one figure can affect the final result. ### 2. A payroll that pays no one [Shadow payroll](https://www.certino.com/shadow-payroll) was another area that was entirely new to me. Before joining Certino, I’d never heard of it. Now it’s something I work with every day. What I find most interesting is how well it reflects the wider challenge of global mobility. An employee may be paid in one country while their tax obligations sit somewhere else entirely, and every one of those obligations still needs to be calculated and reported correctly. ### 3. The rules never stand still I hadn’t appreciated how often the rules change. Legislative updates are remarkably common, and when a programme spans multiple countries, each with its own rules and timetable, there’s almost always something new to account for. The latest [UK Budget](https://www.certino.com/blog/budget-2026-one-budget-two-payrolls) is a good example. The core calculations barely moved, but it still brought significant changes to reporting, including benefits moving onto payroll from April 2027. That’s just one country, and every country in a mobility programme has its own cycle of updates. ### 4. It’s hard to explain in one sentence Outside of work, not everybody I talk to understands what my job involves. Whenever family or people at the gym ask, I always end up repeating myself, which has been a good reminder of how specialist this field is. It’s also helped my own understanding. Finding simple ways to describe what we do has made me think more carefully about how it all works. ### 5. The expertise behind it Above all, my first few months have given me a great deal of respect for the people who work in global mobility every day. Keeping track of changing rules across many countries, managing multiple layers of tax and getting the detail right for every employee takes real expertise. If these areas are complex for someone working alongside tax specialists every day, [it’s easy to understand why mobility teams, who often manage them alongside many other responsibilities, can find them challenging](https://www.certino.com/blog/six-signs-its-time-for-a-managed-shadow-payroll-service). ### New to global mobility too? If you’re also new to the industry, I’d be interested to hear what has stood out to you. And if you’ve worked in global mobility for years, I’d welcome your perspective. You can message me on [LinkedIn](https://www.linkedin.com/in/zak-haralambous-7a4959337/). Share [mailto:?subject=What+I%E2%80%99ve+learned+about+global+mobility+so+far&body=https%3A%2F%2Fwww.certino.com%2Fblog%2Fwhat-ive-learned-about-global-mobility-so-far](mailto:?subject=What+I%E2%80%99ve+learned+about+global+mobility+so+far&body=https%3A%2F%2Fwww.certino.com%2Fblog%2Fwhat-ive-learned-about-global-mobility-so-far) ![](https://www.certino.com/hubfs/zak-haralambous.png) ### Zak Haralambous Zak Haralambous is a Customer Success Associate at Certino, where he works closely with clients to get their data and calculations right first time. He joined in 2026 and is enjoying every surprise the world of global mobility throws at him. [← All articles](https://www.certino.com/blog) ## More from the Certino blog [![alt](https://www.certino.com/hubfs/what-ive-learned-about-global-mobility-cover.png)](https://www.certino.com/blog/what-ive-learned-about-global-mobility-so-far) 02 November 2026   |   [Global Mobility](https://www.certino.com/blog/tag/global-mobility), [Shadow Payroll](https://www.certino.com/blog/tag/shadow-payroll), ##### [What I’ve learned about global mobility so far](https://www.certino.com/blog/what-ive-learned-about-global-mobility-so-far) [![alt](https://www.certino.com/hubfs/budget-2026-post-budget-brief-cover.png)](https://www.certino.com/blog/budget-2026-one-budget-two-payrolls) 28 October 2026   |   [Compliance](https://www.certino.com/blog/tag/compliance), [Global Mobility](https://www.certino.com/blog/tag/global-mobility), [International Tax](https://www.certino.com/blog/tag/international-tax), ##### [Budget 2026: one Budget, two payrolls](https://www.certino.com/blog/budget-2026-one-budget-two-payrolls) [![alt](https://www.certino.com/hubfs/six-signs-managed-shadow-payroll-cover.png)](https://www.certino.com/blog/six-signs-its-time-for-a-managed-shadow-payroll-service) 13 October 2026   |   [Shadow Payroll](https://www.certino.com/blog/tag/shadow-payroll), [Process Change](https://www.certino.com/blog/tag/process-change), ##### [Six signs it’s time for a managed shadow payroll service](https://www.certino.com/blog/six-signs-its-time-for-a-managed-shadow-payroll-service) Book a call ## Talk to a shadow payroll specialist A short call to look at how you run shadow payroll today and where Certino fits. 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