When is an offer binding?

Once you have accepted an offer, you are bound by your acceptance and it is not allowed to cancel the transaction in favor of a better bid. Therefore, do not accept an offer unless you are sure that you can and will sell it. This way, you make sure that neither you nor the seller has a bad experience.

Although, as a rule, a transaction is binding, there can be different reasons, that might hinder the transaction. In special cases of this, it is okay to cancel the transaction, but make sure to always inform the buyer. Read more about this in the link under here.