What is a pre-auth?
Every transaction starts with a pre-auth. This checks that you have the funds available. The actual transaction will come through within a couple of days. Until that time, the pre-auth’d amount will be blocked on your card. In some situations, e.g. opening a tab at the bar, a fixed amount is pre-auth’d to cover what you could spend. Your final bill is likely to be less. It will take up to 10 days for the difference to unblock on your card.
