Designing Tax from the Start: Why Timing Matters in ERP Modernisation

In many ERP programmes, tax is simply introduced too late. A white paper from Harvard Business Review Analytic Services, Building Tax Determination into ERP Modernisation, notes that tax is still too often treated as a downstream consideration rather than a core design requirement, despite its direct impact on system performance and business outcomes.  

By the time tax requirements are fully understood, core system decisions have already been made, from data structures to integrations and workflows. At that point, what could have been designed into the foundation becomes something teams have to retrofit. That shift – from design to retrofit – is where complexity begins, leading to rework, project delays and increased cost as teams try to adapt systems that were never built to support tax requirements in the first place.

Tax Is a Design Decision, Not a Downstream Requirement

Tax is embedded in how transactional data is structured, processed and governed across the business. Every financial transaction carries a tax implication, which means decisions about data models, integrations and workflows directly affect how tax is applied at the point of transaction. If the underlying data and logic are not structured correctly, tax cannot be calculated consistently or accurately.

Compliance builds on that foundation. Reporting, filing and audit readiness all depend on whether tax was determined correctly in the first place. As the Harvard Business Review Analytic Services white paper highlights, increasing regulatory complexity and real-time reporting requirements are placing new pressure on how tax is calculated and managed within core systems. The impact becomes even more visible under real-time compliance and e-invoicing requirements. Organisations are increasingly expected to submit tax-relevant data in real time, demanding fast, accurate and consistent transaction data, often at high volumes and with little tolerance for error. If your ERP environment was not designed with tax in mind, even small inconsistencies in data or logic can lead to incorrect tax calculations, processing delays or compliance gaps.

How Delayed Tax Affects Teams

Timing issues rarely exist in isolation. In many organisations, tax, IT and finance operate with different priorities, timelines and definitions of success. Without early alignment, tax requirements tend to surface after key decisions have already been locked in. This disconnect is reflected in Vertex research, How IT, Tax and Finance Misalignment Is Putting Revenue at Risk, where 31% of organisations report that poor collaboration leads to data challenges, wasted spend or reduced business agility. When that happens, tax is no longer shaping how the system is designed; it is adapting to design choices made without full visibility into compliance needs. This creates downstream pressure across teams, affecting invoicing accuracy, increasing manual workarounds and introducing risk into revenue and reporting processes.

What This Means for Your ERP Modernisation Strategy

Tax is no longer operating alongside finance and IT as a separate downstream function; it is becoming part of the digital core, shaping how systems are designed and how data flows across the enterprise. (I explored this perspective further in a recent blog, Why CFOs Should View Tax Technology as Core Finance Infrastructure.) For you, this means ERP success is not just about selecting the right platform or meeting implementation milestones; it depends on whether tax is built into your design decisions before critical elements are finalised.

The Harvard Business Review Analytic Services paper shows what changes when tax is designed in early versus where organisations face risk when it is not. Explore the findings in Building Tax Determination into ERP Modernisation to see how early design decisions can help you reduce risk, improve accuracy and scale with confidence.