It's possible that you may invite someone to take the IBI survey will take advantage of your invitation. Whenever you like, you're able to convert any survey invitation you've sent back into a seat credit on your account. There are a few ways to do this.

1) Edit Group - If you're on the IES dashboard and click on the name of your survey group, you'll arrive on the Edit Group page. Next to the name & email of anyone who hasn't yet started their survey, you'll see a minus sign ( - ).  Clicking on this minus sign removes their invitation from this survey group and converts the invitation back into a survey credit that you can use for some later survey group invitation.

2) Reclaim All - From the dashboard, you could choose to refund every unused invitation in a single survey group by clicking on the Reclaim All icon. 

3) Run Report - If you're on the Run Report page, generating reports, you can also refund seats from this page for anyone who didn't complete the survey. There's a Reclaim Unused Seats button at the top of the table that functions like the Refund All icon, or you can refund seats individual by clicking the "Reclaim Seat" link next to any qualifying individual.