An enterprise with 60 accounts cannot attribute $2M monthly spend to business units, projects, and environments. Teams use inconsistent tag spellings and billing shows unallocated costs. Finance needs enforceable chargeback by next quarter. Which tagging strategy for cost allocation provides accurate visibility?

The correct strategy succeeds because it addresses the entire allocation chain for 60 accounts: standardized keys and values for business unit, project, and environment fix inconsistent spellings, tag policies centralize definition and compliance checking, SCPs block untagged or mistagged provisioning to make chargeback enforceable by next quarter, and activating billing cost allocation tags propagates those tags into the Cost and Usage Report and consolidated billing to eliminate unallocated costs and attribute the $2M spend. The voluntary-compliance approach fails on enforceability because well-defined and activated tags still depend on human consistency, so drift and missing tags persist and Finance cannot guarantee complete chargeback. The account-grouping approach fails on granularity because allocating by linked account in Organizations reveals business-unit totals but cannot separate projects or environments sharing the same accounts, leaving the stated visibility need unsatisfied. The enforcement-without-activation approach fails on billing integration because policies, SCPs, and remediation govern deployment yet unactivated tags do not appear for cost allocation, so reports continue to show unallocated spend. An exam caveat is to treat tag definition, enforcement, and billing activation as three distinct required actions, where Cost Explorer filtering alone does not substitute for activation. As a practical check, verify the three tags show Active under Billing cost allocation tags, review tag-policy compliance across all accounts, and test that an SCP denies a mistagged launch in a nonproduction account.