We have taken enough time and done through analysis to seek out the minimal permission set required to run effective audit against your AWS account.
arn:aws:iam::aws:policy/SecurityAudit arn:aws:iam::aws:policy/ReadOnlyAccess
account:GetAccountInformation s3:ListBucket lambda:GetFunction dynamodb:DescribeTableReplicaAutoScaling sns:GetSubscriptionAttributes cloudwatch:GetMetricStatistics cloudwatch:ListMetrics billing:Get* payments:List* budgets:Describe* budgets:View* ce:Get* ce:Describe* ce:List* cur:Describe* cur:GetUsage* pricing:* account:GetAccountInformation savingsplans:Describe*