private function save_refund( $post_id ) {

		// phpcs:disable WordPress.Security.NonceVerification.Missing -- Nonce is verified in the save() method of this class.

		$txn_id = llms_filter_input( INPUT_POST, 'llms_refund_txn_id', FILTER_SANITIZE_NUMBER_INT );
		$amount = llms_filter_input_sanitize_string( INPUT_POST, 'llms_refund_amount' );
		if ( empty( $txn_id ) ) {
			return $this->add_error( __( 'Refund Error: Missing a transaction ID', 'lifterlms' ) );
		} elseif ( empty( $amount ) ) {
			return $this->add_error( __( 'Refund Error: Missing or invalid refund amount', 'lifterlms' ) );
		}

		$txn = new LLMS_Transaction( $txn_id );

		$refund = $txn->process_refund(
			$amount,
			llms_filter_input_sanitize_string( INPUT_POST, 'llms_refund_note' ),
			llms_filter_input_sanitize_string( INPUT_POST, 'llms_process_refund' )
		);

		if ( is_wp_error( $refund ) ) {
			$this->add_error( sprintf( _x( 'Refund Error: %s', 'admin error message', 'lifterlms' ), $refund->get_error_message() ) );
		}

		// phpcs:enable WordPress.Security.NonceVerification.Missing

	}