CEI, DSO, and Best Possible DSO: which one tells you collections is working

Most software finance teams run on DSO and hope it goes down. DSO is a fine scoreboard. It's a terrible steering wheel—it moves for reasons that have nothing to do with your collectors, and it hides the difference between a team that's collecting well and a customer base that just pays on time. The metric credit managers are actually reviewed on is the one almost nobody tracks: Collection Effectiveness Index.

What each metric actually measures

• DSO (Days Sales Outstanding): average days it takes to turn sales into cash. Mix-sensitive—one large customer on Net-90 moves it more than a hundred collectors could.
• Best Possible DSO: DSO calculated only on current, non-delinquent receivables. It tells you your floor—what DSO would be if every dollar were collected the day it was due.
• CEI (Collection Effectiveness Index): how much of the receivables that were collectible during a period you actually collected. The gap between CEI and 100% is the money your process is leaving on the table.

Why CEI is the number your collectors should be measured on

CEI is calculated as: beginning receivables plus monthly charge sales, minus ending receivables, divided by beginning receivables plus charge sales, minus ending current receivables. The formula looks like homework. The insight is simple: CEI isolates collection performance from sales volume and payment terms. When DSO rises, you don't know if collections slipped or a customer signed Net-90. When CEI falls, collections slipped. Full stop.

That's why the credit managers who run their teams on CEI can defend their results to a CFO. DSO went up because the sales team closed a $2M annual contract on Net-90 terms—congratulations, not a collections failure. CEI tells you what your team actually controls.

Reading the gap between DSO and Best Possible DSO

The spread between your actual DSO and your Best Possible DSO is the delinquency tax. Every day of that spread is aged, uncollected receivables—the exact pool where recovery odds decay fastest. A wide gap with a stable CEI means the problem is upstream: terms are too long or credit is too loose. A falling CEI means the problem is in the work: accounts aren't being escalated, documented, or placed when they should be.

Where placement fits in the metric

CEI rewards what we do for a living: converting delinquent receivables into cash. An account that crosses 90 days with no payment and no plan is a CEI drag until someone acts. Placement is the action that converts it—and because we work on contingency, the cost of that action is zero until it works. If your CEI has been drifting, the fastest fix is a placement trigger: the day an account hits 90 days with no response, it goes to a specialist instead of the "one more reminder" folder.

Run the CEI calculation on your last two quarters. If it's under 90, there's cash in your aging report that your current process isn't reaching.