The basic requirements are found here: Pulling Charges for Billing (Charge Processing)

One-time Charge Payment on a Check Pledge has some special rules.  Charge Processing will attempt the charge once only, so, if rejected the original pledge must be adjusted again to reenter the one time charge information.

For an explanation of why pledges may be charged a few days earlier or later, see How many days are there between credit card charges?

If you are still unsure why the credit card was not charged, consider the following scenarios: