The mental model that budget policies are for cost and tags are for organization is outdated. For serverless workloads, both job-level tags and budget policy tags flow into system.billing.usage.custom_tags, with budget policy tags winning on key conflicts. The Jobs UI text describes intent but understates the billing reality.

1. DAB job tags appearing in custom_tags without a budget policy. By-design, not a bug, and not DAB-specific. Tags set on a serverless job propagate to custom_tags regardless of whether the job is created via UI, API, DAB, or Terraform. The DAB job schema also accepts budget_policy_id at the job level if you want admin-controlled tags layered on top, see the DAB resources reference. One caveat: jobs/submit one-time runs don't propagate tags, only jobs/create and jobs/update. If you saw different behavior earlier this year, propagation has been consistent for some time now.
   
   
2. Budget policy field missing from UI for some serverless job types. Three different reasons depending on the case. 
   
   For DAB-deployed jobs, the UI hides most settings (including budget policy) because DAB jobs are deployed in UI_LOCKED mode by design. See this KB article. Set budget_policy_id in your bundle YAML.
   
   For Terraform-deployed jobs that wrap a Lakeflow Declarative Pipeline, you're hitting a documented limitation on top of the IaC UI lock: per the budget policies docs, "Pipelines triggered by jobs do not inherit the job's serverless usage policy. Users must set the pipeline's policy." Configure the policy on the pipeline directly.
   
   For ClickOps-created managed ingestion jobs (Salesforce, etc.), the budget policy selector has known display gaps in the ingestion wizard context. Workaround: open the underlying ingestion pipeline and set the policy there.
   
   Net rule: when a job's compute is actually a wrapped pipeline (DLT, managed ingestion), the budget policy belongs on the pipeline, not the job. When the job itself is serverless and IaC-managed, set it in YAML/HCL.
   
   
3. Tags element inside Budget Policy showing blank when tags are set. Display bug, billing attribution is not affected. The renderer keys off the job's explicit settings.budget_policy_id field, but certain UI patches can leave that field empty even though effective_budget_policy_id is still set under the hood. Tags continue to land in system.billing.usage.custom_tags correctly. Workarounds: re-select the policy in the dropdown to repopulate the explicit field, and verify directly with:

SELECT custom_tags, usage_metadata
FROM system.billing.usage
WHERE usage_metadata.job_id = '<job_id>'

A related and documented limitation: budget policy tags also don't render on the Jobs list view, only on the Job Details page (same docs page, "Known limitations").

On the broader question, how to think about serverless cost tagging. A "cost tag" in Databricks is anything that lands in system.billing.usage.custom_tags. For serverless that column is the union of budget policy tags (admin-set, win on key conflicts), job-level tags (practitioner-set via UI/API/DAB/Terraform tags field), pipeline tags (set on the DLT or managed ingestion pipeline), and inherited workspace tags. Treat the two main mechanisms as complementary: budget policies for governed admin-controlled attribution that practitioners can't override (cost center, department, environment); job tags for practitioner-managed metadata that also shows up in billing as a bonus (project, team, ticket-id); pipeline-level policies for anything wrapped by a job. The tag attribution docs cover propagation rules end-to-end if you want the full read.