As with many other merchants, the iTunes Store and Mac App Store places an authorization hold on your payment card account for the approximate amount of any purchase you make. If you update your billing information, the iTunes Store or Mac App Store will place an authorization hold on your payment card account, usually in the amount of 1 USD or the local currency equivalent, to verify your account information.
You might see authorization requests on your online statement. These requests aren't actual charges; they are tests to confirm that your payment card account is active and has available funds to accommodate transactions. Authorization holds are removed by your financial institution shortly after your purchase clears. The time it takes to remove authorization requests varies by financial institution.
To review the actual charges on your account, see your iTunes Purchase History. You will be asked to enter your iTunes account name and password. (You can only see Mac App Store web order details in your iTunes purchase history.) Your Purchase History will display your most recent purchases first. To view details of any purchase, click the arrow to the left of the order date.
If you have questions about the way your financial institution handles authorization requests, contact their customer service department.