Delivered is not payable
Activity moves through states: delivered, validated, in the buyer's review window, then approved or rejected, then paid. The gap between delivering a transfer and receiving money for it is normal and is defined by the review window plus the payment schedule. Centers that plan cash flow around delivery rather than approval run into trouble in their first month.
The review window
Buyers get a defined period to reject activity that does not meet published criteria, with a stated reason. Unreviewed activity typically auto-approves at expiry. Your dispute window runs separately and is usually shorter, which is why rejections need attention promptly rather than at month end.
Holdbacks and clawbacks
Some campaigns hold a portion of payout until a quality period passes, particularly in sale and application models where cancellations occur after the fact. Clawback provisions allow recovery of amounts already paid on activity later determined invalid or fraudulent. Both should be stated explicitly on the campaign before you accept it.
What actually determines your effective rate
Headline rate multiplied by approval rate, minus the time value of the payment delay. A campaign paying less per transfer with a ninety percent approval rate usually beats one paying more at sixty percent, and it is far less volatile to staff around.