When you sign up for a free trial, Skype authorizes your credit card or PayPal account for the nominal amount of €1/£1/$1 (or similar amount in your currency), to check that the payment method is valid, and so that we can validate the person participating in the promotion. You may also need to verify your credit card using either Verified by Visa or MasterCard SecureCode verification.
Don't worry – you won't actually pay this amount. It's possible that you will see it as a Pending transaction on your bank statement for a couple of days, but as soon as your payment method has been authorized, we cancel the charge.
You can always contact your card issuer for confirmation or to ask for additional information about this transaction.