Margin erosion doesn't happen in one jump — it compounds across dozens of small price lifts, each one defensible in isolation. By the time you notice, you're 4–7% behind where you budgeted.
The three questions, per supplier, every quarter
- What did we pay per unit for our top five SKUs this quarter versus last quarter? Pull three invoices from each period and compare line by line.
- Did they notify us in writing before any increase? Most supply agreements require 30 days' notice. Most suppliers skip it.
- Have we tested their price against two others in the past six months? If no, add them to the rotation list.
What it catches
The quiet 8% lift on your number-two protein. The fuel surcharge that never came off. The supplier who assumes you're not watching. You don't need to switch — the conversation alone usually resets the behaviour.