Following our last post, where Mike shared how two clients (his now-famous “London buses”) asked the exact same question about in-house tax expertise, one thing quickly became clear to me: the conversation does not stop at, “Should we do this?”.
In this blog post, we’re exploring the next question:
What are the real pros and cons?
At first glance, the role of an in-house Mobility Tax Advisor can sound like an obvious win. However, the reality we see with clients is more nuanced. Some programs genuinely unlock significant value, while others struggle to justify the investment. Most mobility programs sit somewhere in between.
So, rather than trying to land on a simple yes-or-no answer, let’s look at what we’re consistently hearing from mobility leaders.
Where does this role really add value? And where do the challenges tend to show up?
As highlighted in the previous post, large, complex programs often benefit the most from building in-house tax expertise. But as mobility programs evolve, many organizations are weighing this option against continued reliance on external providers.
While the potential value is clear, the decision is rarely one-size-fits-all. It depends on a range of factors, from company culture and mobility strategy to program complexity and policy design.
With that in mind, below is a practical breakdown of the key pros and cons, based on what we’re seeing in the market today, to help guide your thinking.
Rather than thinking about the benefits in isolation, the real question we hear from Mobility leaders is:
“Where does this actually make a meaningful difference in my program?”
The value of an in-house tax advisor tends to show up differently depending on the scale, complexity, and operating model of your mobility program.
Here’s how that plays out in practice:
For organizations with high volumes, multiple assignment types, and global footprints, this is often where the role delivers the most immediate and measurable value.
In these environments, an in-house advisor can:
Act as a central control point across hundreds of cases
Reduce fragmented communication with tax partners
Drive consistency in how tax is applied across regions and policies
Identify cost leakage at scale (e.g., TEQ, shadow payroll gaps, redundant services)
At scale, even small inefficiencies multiply quickly. This role helps standardize decisions (tax approach, payroll set up, TEQ policy) and control costs across the entire program, not just on individual cases.
If your program relies heavily on external tax providers, an internal advisor becomes a lever to reshape costs, not just reduce.
They help:
Filter and prioritize what truly needs external advisory
Reduce iterative back-and-forth with providers
Challenge and validate external advice where appropriate
Support smarter scoping of services
Organizations don’t eliminate tax partners but instead they use them more selectively and strategically, often reducing unnecessary spend while improving outcomes.
Programs that benefit significantly from inhouse tax expertise during decision-making and assignment planning include:
Expanding into new regions
Moving beyond traditional assignment types
Programs dealing with frequent exceptions
Advise in real time on different structuring options
Help the business understand trade-offs (cost vs. experience vs. compliance)
Move decisions upstream—before tax becomes an issue
This is one of the most underappreciated but high-impact areas.
Where organizations have:
Aging TEQ balances
Low tax payment recovery rates
Ongoing employee disputes
…the presence of an internal advisor can significantly tighten processes.
They can provide:
Ongoing oversight (not just year-end involvement)
Direct engagement with stakeholders and assignees
Internal accountability for collections and reconciliations
Less “leakage,” stronger controls, and measurable improvement in financial recovery over time.
In companies where Mobility, Payroll, Finance, and Corporate Tax operate in silos, the biggest value is often organizational, not purely technical.
An in-house advisor becomes:
A translator across functions
A consistent voice in planning conversations
A connector between internal teams and external providers
Many mobility challenges aren’t purely tax issues - they’re alignment issues.
This role helps eliminate friction that otherwise slows decisions or creates risk.
Of course, as with most things in mobility, it’s not all straightforward. Here are some challenges where organizations may pause or hesitate to hire an in-house tax advisor.
Even when the value is clear, making space for an additional role isn’t always easy.
There might be challenges around:
Justifying adding headcount to Mobility in cost-sensitive environments
Budget ownership sitting outside the function
Relocation (including external tax) costs are often passed through to the business unit which makes it more complex to allocate the cost of an in-house tax expert
Reality: The upfront cost can be a barrier, even with long-term savings.
Another common concern is how risk is perceived and managed.
What this means in practice: Clear governance, role definition, and boundaries become even more important.
This is one of the biggest determining factors. Not every program will benefit equally:
Simply Put:
The business case depends heavily on scale and complexity. The more complex and varied the program, the stronger the case tends to be.
Even the most experienced in-house tax advisor won’t be an expert in every tax jurisdiction. Typically, Global Mobility tax roles are filled with tax professionals that often bring a background in Finance having worked for one of the Big 4 accounting firms.
That means:
This is one of the more practical but often underestimated challenges.
Questions we hear frequently include:
From experience:
Getting this right early on makes a significant difference to long-term success.
The most effective mobility programs don’t eliminate external providers. Instead, they optimize how they use them.
They take a balanced approach by:
Building internal capability where it adds the most value
Using external providers more selectively and strategically
Creating a more efficient and connected overall model
If there’s one thing that stands out from all these client conversations, it’s this:
There isn’t a single “right” answer.
The decision to bring tax expertise in-house really comes down to:
The complexity of your program
Your cost structure and current consulting spend
Your organization’s appetite for investment and risk
Your business culture
But when the conditions are right, this role can become much more than an additional resource. It can fundamentally change how mobility decisions are made and how effectively organisations deploy talent globally.
If you’re considering whether in-house tax expertise is right for your mobility program, AIRINC can help you assess the business case, evaluate your current provider model, and benchmark your approach against peer organizations. We can also help you identify the right balance of internal capability and external support to meet your organization’s cost, governance, and talent mobility goals.