Your credit card is only charged for a pledge when the campaign you pledged to ends successfully, not at the time of placing the pledge. When you pledge to a project we'll also send you a confirmation email with information about the estimated timing of any potential charges.
At the time of placing your pledge you may see a pending authorization on your statement, however if the campaign does not reach 80% of its funding goal your card will not be charged and that pending line should fall off.
If your card is declined for any reason, you'll receive a notification on how to update your payment details and fix the pledge. This will happen after the campaign is complete.
Please note: If a tip is given alongside a pledge, the credit card will be charged immediately for the tip at the time of pledging.