You can only delete offers that are in draft state. Once the offer is active, it can't be deleted.

However, you can still prevent affiliates from sending traffic to an offer if necessary. To do so, navigate to the Offer detail (open the details of any active offer) and click on the "Deactivate offer" button.

Alternatively, you can click on "Deactivate offer" right from your offer list.

Once the offer is deactivated, affiliates can't access it, and you won't need to pay for conversions generated after the offer's deactivation.