The Customer Concentration Alarm: When Your Best Customer Is Your Biggest Risk

At 33% of revenue, the sample's biggest account sets terms, jumps every queue, and its departure would tear a $205,000 hole that takes two years of the entire new-business engine to backfill — burning $92,000 of margin on the way. And the risk is priced in today: buyers apply a $112,500 concentration haircut whether anyone leaves or not.

How it works

• The Concentration Board — customers ranked, flags at 10% / 20% / 35% ("THE BUSINESS HAS A BOSS"), the top-three line. Nothing here says your big customer is a bad one — they're great, which is exactly how businesses drift into this
• The Loss Math — the margin hole, the backfill clock at your honest new-business rate, and the haircut every buyer and banker applies in an afternoon
• The De-Risk Plan — rule zero: never fire the big customer; the fix lives in the denominator. The next-five target list (24 months of ordinary new business, aimed deliberately, takes 33% to 25%), contract terms that make leaving loud, the embed moat (accounts leave vendors; they almost never leave infrastructure), and the annual margin-and-attention re-rank that catches concentration wearing a loyalty costume

Built for

Contractors with one big builder · agencies with one big client · makers with one big retailer · every owner whose pulse changes when a certain area code calls.

What you get

One .xlsx file, four tabs, instant download. Excel, Google Sheets, Apple Numbers, LibreOffice. No macros, no subscription.