It is not possible to pay twice in error. This is because when the payment has been made, a green tick automatically appears on the homepage of your Application Space next to the link to pay the registration fee. This tick is a visual sign that tells you that your payment has been saved. If, despite this, you still click on the link again to pay, the payment form will not be displayed.
If, despite everything, your bank statement shows that you have paid twice in error, then send us a copy of your bank statement so that we can check it out.