Judy sends invoices to clients with time and materials (vs. fixed price) projects at the end of every month.
Project Managers review the line items in the invoice to ensure that the billing is accurate.
To avoid surprises at the end of the month Project Managers should be reviewing time entries in Harvest weekly to ensure that time has been logged to the correct project, no entries are missing, and descriptions are included.
Review the monthly invoicing document at the end of each month (don't worry - a reminder will go out over Slack), take a look at the entries and compare hours in Harvest to ensure they're accurate.
If your project requires additional deliverables or documents in order to invoice (such as a monthly report or signed detailed timesheet), make sure to proactively begin to prepare those items before the first of the month.