What is purchasing control for MSPs and why do you need it?

These are the key points

• Purchasing control is the systematic comparison of supplier invoices against contract agreements, services and actual usage.
• Invoice processing books an invoice for the books. Purchasing control checks whether its content is correct.
• A PSA or accounting system does not do this automatically for you.
• Without purchasing control, margins leak away, often without you noticing.
• Automated purchasing control saves up to 80% of the time spent on manual checks (ResalePartners, 2026).
• With 110+ integrations you connect all your relevant suppliers in one platform.

The definition: what do we mean by purchasing control?

Purchasing control is the systematic checking of supplier invoices, contract agreements and variable usage. The aim is to spot discrepancies and errors before they are charged on to your customers. That sounds simple, but in practice it is anything but straightforward for MSPs.

A supplier invoice is rarely one-dimensional. You are dealing with licence changes, variable usage, bundle adjustments and price increases that are sometimes slipped through quietly. Purchasing control means systematically comparing all those invoice lines against what was agreed contractually and what you actually ordered.

The result is a clear picture per supplier, per service and per customer. You know what you are purchasing, for whom and at what cost. Not after the fact, but the moment the invoice comes in.

Why is purchasing control so relevant for MSPs in particular?

MSPs operate with a level of complexity that most other businesses simply do not have. You do not deliver a single product, but a combination of licences, telephony services, workplace management and other subscriptions. Often to dozens of customers at once, through multiple suppliers that each have their own invoice structure.

That complexity significantly increases the risk of errors. A small discrepancy in a supplier invoice, multiplied across hundreds of customers, can cause a substantial margin leak. And that leak often goes unnoticed for months, until you see it reflected in your profit.

Think of:

• Licences that simply keep running at the supplier after cancellation
• Rate changes that are not passed on into your sales price
• Variable usage that turns out higher than expected and is not fully charged on
• Services you purchase for a customer but forget to invoice

For an owner or director, these are direct threats to margin. For the operations manager, it means extra investigative work and errors that lead to disputes with customers. For the financial controller, it is a reliability problem in the reporting.

The difference between purchasing control, invoice processing and a PSA

This is one of the most frequently asked questions. Many MSPs think they already have purchasing control because they use a PSA or because their invoices are neatly recorded in the accounts. That is not the case.

• Invoice processing records and books an invoice for the accounts. It says nothing about whether the costs are actually correct.
• A PSA tool manages tickets, assets and hours. It is not built to assess supplier invoices on their merits or to connect purchasing costs to customers.
• An accounting system processes whatever is booked into it. It does not check whether the purchasing matches what was agreed or delivered.
• Purchasing control does something different: it compares purchase invoices in detail against contracts, services and usage. Discrepancies become visible immediately, before they are charged on.

The three systems do not replace one another. They are complementary. But purchasing control is the link that makes sure everything is right on the buying side, so that your PSA and accounting are fed with reliable data.

What happens if you do not have purchasing control?

Without purchasing control you rely on spot checks, manual reviews and the hope that suppliers do not make mistakes. In practice this leads to a number of familiar problems.

First of all, you lose time. Manual invoice checks cost hours of administrative work every month, work that adds little value but is error-prone. Secondly, you run a financial risk. Discrepancies you do not see are not corrected. That means you either pay your suppliers too much or charge your customers too little, often both at the same time.

On top of that, disputes with customers about invoices become harder to back up if your purchasing is not recorded in a traceable way. And as you grow, the problem gets bigger rather than smaller: more customers, more suppliers, more opportunities for errors.

How does purchasing control work in practice?

With InkoopControle from ResalePartners the process works as follows:

• Purchase invoices are imported automatically via API integrations or CSV import
• The invoice lines are connected to your customer profiles, services and suppliers
• Discrepancies, changes and price differences are flagged automatically
• You get an alert, and only when everything is correct can the invoicing move on to the customer
• Dashboards give you a clear financial overview per supplier, service and customer

The platform supports more than 110 suppliers and platforms, from telecom players such as Gamma, RoutIT and KPN to software suppliers such as Microsoft 365. Is your supplier missing? ResalePartners is happy to add it.

The result is that you no longer have to check things by hand. You see straight away what is off and can adjust before it becomes a problem for the customer or your margin. Want to know how protecting margin as an MSP works in practice? Or how you detect discrepancies in supplier invoices? Then read the other articles in this series as well.

Want to know whether margin is leaking away in your purchasing?

Book a free demo of InkoopControle and check your purchasing in 30 minutes. Our specialists show you where discrepancies arise and how to fix them.

View the full purchasing control for MSPs