The licence page in the Microsoft 365 admin centre is the most expensive page nobody reads.
Six seats assigned to people who left, a shared mailbox and a test account. At $22 a seat that is $132 a month, $1,584 a year, for nothing. It paid for the assessment that found it twice over.
Why it happens
Leavers get disabled but not unlicensed. Shared mailboxes get created as users. Someone buys a seat for a test and never removes it. There is no monthly ritual to check.
The fix is a leaver runbook that includes the licence, converting shared mailboxes properly, and a licence line in the monthly report so it never drifts again. We put that line in every report we send.