Box 1: Assign a tag to each resource.
You apply tags to your Azure resources giving metadata to logically organize them into a taxonomy. After you apply tags, you can retrieve all the resources in your subscription with that tag name and value. Each resource or resource group
can have a maximum of 15 tag name/value pairs. Tags applied to the resource group are not inherited by the resources in that resource group.
Box 2: From the Cost analysis blade, filter the view by tag
After you get your services running, regularly check how much they're costing you. You can see the current spend and burn rate in Azure portal.
1. Visit the Subscriptions blade in Azure portal and select a subscription.
You should see the cost breakdown and burn rate in the popup blade.
2. Click Cost analysis in the list to the left to see the cost breakdown by resource. Wait 24 hours after you add a service for the data to populate.
3. You can filter by different properties like tags, resource group, and timespan. Click Apply to confirm the filters and Download if you want to export the view to a Comma-Separated Values (.csv) file.
Box 3: Download the usage report
Reference:
https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-using-tags
https://docs.microsoft.com/en-us/azure/billing/billing-getting-started