What to Look for When a Supplier Opens Their Books

The invitation to review a supplier's cost base usually arrives in one of two circumstances: a supplier wanting to justify a price increase by showing you why they cannot absorb it, or a buyer in a strategic relationship who has negotiated open-book access as a condition of a long-term contract. In both cases, the experience tends to follow a similar pattern. A slide deck or spreadsheet is presented, key cost lines are shown with varying levels of detail, the figures are explained with confidence, and the buyer leaves the meeting with a general sense of the supplier's cost structure but a specific uncertainty about what to do with it.

This is usually because the wrong questions were prepared, or because the value of an open-book review was understood as seeing the numbers rather than interrogating them. Seeing the numbers is the beginning of the conversation, not the conclusion.

What suppliers present and what they do not

An open-book presentation is a curated document, as all financial presentations are. The lines that appear are the ones the supplier has chosen to show, at the level of aggregation they have chosen to use. The lines that are most informative for a buyer are often the ones that are not shown at all, or shown only as totals, or explained with a confidence that discourages follow-up questions.

Overhead allocation is the most common place where useful information is hidden. A direct cost presentation that shows materials, labour, and logistics, with overhead as a single line or percentage, has concentrated all the interesting commercial information into one number. How overhead is allocated, which cost pools drive it, and whether the allocation is proportional to what your specific work actually consumes — these are questions that a flat overhead percentage does not answer and that most open-book presentations are not designed to make easy.

The questions that produce useful information

The questions worth asking in an open-book review are specific and probing rather than general and appreciative. What does the overhead rate cover, and how is it allocated across different customer accounts or product lines? What has the trend been in each major cost element over the last three years? Where in the cost structure has the supplier absorbed inflation, and where have they passed it through? What would the cost look like at ten percent lower volume, or twenty percent higher?

These questions are not adversarial. They are the questions of a buyer who is trying to understand the real cost basis of what they are buying, which is exactly what open-book access is supposed to enable. A supplier who has offered open-book access and then resists specific questions about allocation methodology or volume sensitivity has not really opened the books. They have opened a summary, which is commercially very different.

What the margin question reveals

The question buyers often avoid in an open-book context is not what the margin is — that is usually either stated or visible from the numbers — but whether it is appropriate given the risk and capital the supplier is committing to this work. A margin that looks high but reflects significant working capital exposure, delivery risk, or technology investment is different from one that is high because the customer base lacks sufficient commercial pressure to test it. Asking what drives the margin, rather than what the margin is, produces a different kind of conversation about whether the cost structure is right.

The point of an open-book review is not to produce a number to argue about. It is to understand the structure well enough to ask the right questions about it, and to maintain the rigour of those questions against a supplier who is presenting the information they have chosen to present. Most buyers exit open-book meetings having seen a great deal and interrogated very little. The discipline of pressing into a line the supplier is reluctant to disaggregate — and holding the question when the response is confidence rather than data — is exactly what Voice2Evolve builds through repeated practice before the real cost review is on the table.

Procurement takeaway

• Prepare a specific list of questions before any open-book meeting — ask for overhead allocation methodology, the cost trend per major element over three years, and volume sensitivity at minus 10% and plus 20%.
• Challenge every overhead presented as a single line or percentage: ask which cost pools it covers and how it is allocated across different customer accounts or product lines.
• Ask what the margin is and what drives it — distinguish between margin that reflects genuine risk and capital exposure and margin that exists because commercial pressure has been absent.
• If a supplier resists disaggregating a specific cost line, treat that resistance as the most commercially significant data point in the meeting and press into it rather than moving on.