You can choose to receive an email notification every time your report runs: *link to ‘Can I have my report emailed to me or my client when it's completed?’ article*
You can also check the status of each report on the Location Dashboard. If it says ‘Updating data...’ under the tool’s name in the sidebar, this means that the report is still running. If this message is not present, the report is ready to be viewed.
In the above example, the Rank Checker report is still running, but the Citation Tracker, Reputation Manager, Google My Business and Local Search Audit reports are ready to view.