If your card is authorized, payment will be taken immediately, and you will receive an email confirming that your order has been successful.
If your card is not authorized, payment will not be taken, and we'll email to let you know that your bank or card issuer wouldn't authorize the payment.
Please remember that even if a payment isn't authorized, it may look like ASOS has taken the money as some card issuers may still reserve the money, for a short period of time.