The 15% cap nobody could explain

Sales asked for a 25% discount to save two big accounts. An engineer found the cap in billing, raised it from 15% to 25%, and shipped it the same day. It was a one-line change.

Three weeks later Finance saw margin below the board’s floor. Two weeks after that, someone finally found out why the cap was 15%. It was protecting that floor. The person who set it had left in March.

Nobody did anything wrong

Sales asked a fair question. The engineer read the system correctly. The code said 15%. It did not say why.

This is the shape of most expensive business-logic mistakes. Not a bug, not carelessness: a correct change to a rule whose reason had quietly disappeared.

The reason was one question away

The person who knew was reachable for months before they left. Nobody asked, because nobody knew there was anything to ask.

Why 15% rather than 20%?

That is the question om asks, to the person who decided, before anyone needs the answer.

What changes when the reason is kept

With the reason kept next to the rule, the engineer sees it before shipping:

Rule	Discount cap 15%
Reason	Protects the board’s margin floor on enterprise deals
Owner	Head of Finance
Status	Approved

The change might still happen. It happens with Finance in the room. In this case Finance would have approved an exception for two accounts instead of raising the cap for everyone.

Where else this is hiding

Every company has a dozen numbers like this: refund windows, credit limits, manual-review thresholds, cool-off periods, retry caps on payouts. Each was set by someone, for a reason, at a moment. Ask your team which of them they could explain today, and who they would ask if they couldn’t.