Many activation partners provide targeted usage reports for Salesforce Audience Studio mutual customers on a monthly basis. These reports are required no later than the 10th day of the month following the close of the previous unreported month (e.g. Report February 2019 usage no later than March 10, 2019).
Usage reports sent directly from Activation Partners must be provided in Salesforce Audience Studio required format as described here.
In the platforms where impressions targeting against 2p and 3p data is supported, but the activation partner does not report directly, customers must follow the instructions to report via their Salesforce UI account here.