Billing Instances Separately

Hi, @Karvesh

You can't.
(However, it may be supported depending on the billing agency vendor.)

As an alternative, you can use the cost allocation tag to keep track of the usage charges for each instance.
https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/cost-alloc-tags.html

If you want to separate it as an invoice, you need to separate the account.