When billing for Microsoft CSP or AWS Reseller, there are 2 simple rules to follow in order to select an optimal bill date.
For AWS Reseller accounts - billing in AWS occurs at the end of the month, but may take 4-5 additional days to finalize. We recommend setting bill dates for AWS Reseller accounts for the 6th of every month, or later. Billing will be done for the month prior.
For Microsoft CSP (Azure and Office365) accounts - billing varies depending on the date you signed up for PartnerCenter. In order to find your billing date, go to PartnerCenter, click on Billing on the left menu and look for your bill date. We recommend setting billing in Unigma at least 4 days after your PartnerCenter billing date.