Data & Analytics

Spend data categorization: selecting a spend taxonomy

Toni Tikkanen Nov 19, 2020

Spend categorization does not have to be painful. Granted, it can be time-consuming and demanding, but the time spent on developing a robust category structure will pay off handsomely. Extracting usable information from historical company spend data sounds easy in principle but in practice it can be challenging. Without a firm foundation, the information you generate from the raw data may be incomplete, error-ridden and unreliable.


Let’s start with a spend categorization structure that’s customized to your business. Spend is classified based on a hierarchy of categories, from general to specific, and extends down by up to 6-7 levels of granular detail. Though it’s possible to extend the hierarchy beyond 4 levels, we find that last levels are often either repetitive or an unfeasible level of granularity in terms of the categorization effort required. A good rule of thumb is that the last level of the taxonomy should be able to be sourced with a single RFP.

Curious how spend taxonomies can fuel your Spend Analysis projects: read this guide!

This hierarchy is also called a taxonomy or a category tree - which is an essential part of the science or technique of spend categorization (also called spend classification). Here is a simple example of a taxonomy for professional services:



Why is spend categorization so important?

The main objective is to provide a base for identifying strategic sourcing initiatives. Attention to taxonomy design is very important because it helps to classify your data accurately so that you can see what you’re spending on, how much, to whom and what the scope for cost savings is.

Making informed decisions based on your spend is only possible when the data is complete, cleansed and allocated into meaningful buckets. These buckets must be relevant and meaningful in your industry sector and your organization. The categories selected must be accepted and commonly understood by every level of management across all business units. If the categorization is too complicated it will create confusion; if it’s too simple, opportunities will be missed. Everyone needs to be talking the same language.

What to consider when designing your taxonomy 

  • Align your categories with business needs, including internal reporting requirements
  • Create a hierarchy with enough sub-categories within a category to be useful. If the spend data is grouped at too high a level, there may be savings opportunities missed. Too many levels may mean that sub-categories with small amounts of spend become timewasters.
  • The taxonomy or category tree should be structured from a supply market perspective  to consolidate spend from suppliers of similar goods and services. Take advice from subject matter experts to ensure that your categorizations make sense and that they are complete, valid and accurate.
  • A common mistake in selecting category taxonomy is that category should explain what goods or services were purchased, not who purchased them, what the source was, or which accounting process the purchases belong to. Rather than categorizing spend data based on these factors, they can be included as additional data points so that they can be used in analysis.
  • Categories and sub-categories must be unique and not duplicated in another part of the taxonomy. Each sub-category must be mutually exclusive, e.g. if auditing is a sub-category in Financial Services it must not also appear as auditing under Accounting and collectively exhaustive, meaning all types of spend must have a place in the taxonomy.
  • Categories must be clearly defined, agreed upon, documented and communicated. Thought must be given to the coding norms – numbers, naming conventions and length of descriptions at each level.
  • Consider expanding growing categories with additional sub-categories e.g. mobile technology and hand-held devices within I.T. hardware.
  • Avoid having a category named “other”. All spend belongs somewhere.


Using an existing taxonomy vs a customized one

Developing your customized category hierarchy can be laborious but is time well spent. This is especially true for direct categories where spend tends to be very different across different companies, less so for indirect spend which has much more commonalities across companies.

The United Nations Standard Products and Services Code (UNSPSC) is an example of a well-known taxonomy of products and services. It is a four-level hierarchy using eight-digit numbers, with an optional fifth level. UNSPSC is an extensively used taxonomy of products and services, but it is not ideally suited to strategic sourcing. Other examples Standard Industrial Classification (SIC) and North American Industrial Classification System (NAICS) and the European NACE (Nomenclature of Economic Activities) codes but none of these is entirely satisfactory. Companies also have their general ledger (GL) codes, used by finance but usually not the best fit for procurement’s needs.

At Sievo, we recommend a hybrid solution that’s developed to fit a company’s needs, combining existing taxonomies  and tweaking them to support the buckets of spend that generate insights.


Tips to move towards a better taxonomy

  • Align your category hierarchy to your supply market
  • Use specialist knowledge and expertise to help with defining category groups
  • Utilize a software solution with flexible taxonomy capabilities that lets you use whatever structure you want: GL codes, your accounting system, SAP codes or any combination of these.
  • Take advantage of software to help granularly classify your data.




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