How can I change my subscription from 10 users to 5 users in Quickbook Desktop Enterprise?

Their billing system is very rigid. You need to cancel your subscription and purchase a new one. If you are not located in Canada, you can purchase it via a partner.

Hello speedmoney,

Welcome to Community!  To ensure your QuickBooks Desktop subscription meets your business needs, I encourage you to contact our Customer Care team outside of this forum.  They will be able to assist you with managing your subscription, so you can get back to business as soon as possible!

If you have other questions, please don't hesitate to reach back out.  We would be glad to help!