THE Group for Authors! discussion

They have certain time frames where you can opt out. If you go to your KDP dashboard and click on the book of choice. Within there is information.
Directly copied from site: "Note that the KDP Select enrollment cancellation period ends on the date of your first free promotion or three days from enrollment, whichever is earlier."

H.R. wrote: "Quick question: Does anyone know if I can leave KDP Select early, so I can start putting my stuff on Smashwords? Or is it that KDP Select has exclusive rights to my work, and I can't start using Sm..."

No. You're stuck with Select throughout 90 days. I recall there were a few authors in the early days of Select who got punished for putting up books at other retailers a couple of days early before their term was up. Got their books pulled from the Kindle store. So I wouldn't advise doing what you're suggesting until your full 90 days has expired. Amazon has ways of knowing if you violate your TOS. So it's best to play by the rules and ride out your days. Just make sure to untick the check mark in the renew box so that you don't accidentally reenroll in Select.

It's a contract you've signed with KDP, so, like with any contract, you are obligated to fulfill your part.