Company A purchases company B and inherits three new AWS accounts.

Implement AWS Organizations and create a service control policy that defines the billing relationship with the new master account.

Configure AWS Organizations Consolidated Billing and provide the finance team with IAM access to the billing console.

Send Cost and Usage Reports files to a central Amazon S3 bucket and load the data into Amazon Redshift. Use Amazon QuickSight to provide visualizations to the finance team.

Link the Reserved Instances to the master payer account and use Amazon Redshift Spectrum to query Detailed Billing Report data across all accounts.