False Claims Amendments Act of 2021 This bill revises procedures under the False Claims Act (FCA), a law that rewards whistleblowers (known as relators) who bring claims on behalf of the government by allowing them to share in the recovery in cases where the government recovers funds lost to fraud. To be recoverable under the FCA, a fraud must meet, among other conditions, standards for materiality. In determining materiality, the decision of the government to forego a refund or to pay a claim despite actual knowledge of fraud or falsity shall not be considered dispositive if other reasons exist for that decision with respect to such refund or payment. In dismissing an action over the objections of the relator, the government must identify a valid government purpose and a rational relation between dismissal and accomplishment of the purpose. The relator must have the opportunity to show that the dismissal is fraudulent, arbitrary and capricious, or contrary to law. The bill extends relief from retaliatory actions to former employees. The Government Accountability Office must report on the effectiveness of the FCA.