You bought 42 seats. You billed 38.
Nobody noticed for nine months.

Drop in your Microsoft reconciliation file and your invoice export. This tells you every licence you're paying for and not charging a client for.

Your files never leave this page. No upload, no account. The matching runs in your browser. Close the tab and it's gone. Check the network tab if you like.

The two files

CSV only. If it's Excel, Save As → CSV first. Drop them in either box, it works out which is which.

Haven't got the files to hand? Run it on sample data. Six invented clients, one real mess.