A CloudOps engineer needs to ensure that AWS resources across multiple AWS accounts are tagged...

AWS Organizations Tag Policies provide a centralized, scalable governance mechanism to standardize tagging across accounts. Tag policies let an organization define tag keys, allowed values, and tagging expectations, helping teams apply consistent tagging conventions across many accounts without building custom logic. This matches the requirement for consistent tags “across multiple accounts” with minimal operational overhead, because the policy is managed centrally and applied at the organization/OUs level.

For cost tracking, user-defined tags must be activated as cost allocation tags in AWS Billing and Cost Management. Enabling cost allocation tags is the required step to make those tags usable in billing views (for example, Cost Explorer allocation and reporting). Combining Tag Policies (governance/consistency) with cost allocation tag activation (billing attribution) directly meets both parts of the requirement.

Option B (CloudTrail + Lambda auto-tagging) is higher operational overhead: it requires event processing, permissions, continuous maintenance, exception handling, and careful logic to avoid incorrect tag assignments. Option C is partially relevant for compliance detection, but AWS Budgets does not “apply tags” to resources; Budgets is for cost/usage alerts and budget tracking. Option D can enforce tagged provisioning paths, but it’s not comprehensive for all resource creation mechanisms and Trusted Advisor is not a global “tag enforcement” engine.

Therefore, A is the most native and least-ops approach for consistent tags across an organization and enabling cost allocation tracking.