The district court erred in granting defendant summary judgment in this False Claims Act case. A genuine issue of triable fact existed as to whether defendant’s use of the “KX” modifier in its Medicare reimbursement claims was material. The modifier indicated compliance with local coverage determinations. That certification was false, and it would be material if the trier of fact concluded from the disputed evidence that Medicare would not have paid the claim had it known the true facts–which required a case-by-case review of the outcomes of the use of defendant’s medical device.