No. The billing invitation and reminder emails that Procore sends to your subcontractor are courtesy notifications designed to notify them when a new billing period has been created and the due date for that billing period is nearing. As long as your subcontractors meet the requirements detailed in Submit a Requisition as a Subcontractor, they can submit a requisition at any point between the creation of a new billing period and its due date.
How is a billing invitation sent?
When a representative for a general contractor creates a new billing period, they have the option to send out an automated billing invite to anyone who is either (1) named on the 'Private' list for the requisition or (2) a member of the Commitment tool's default 'Requisition Distribution' list. See Start a New Billing Period and Send Requisition Emails and Create a Requisition Billing Distribution.
What do I do if a subcontractor reports that the billing invitation is lost or missing?
Should one of your subcontractors report that they do NOT have a copy of the billing invitation, they can simply log in to Procore, navigate to the Commitments tool, and then follow the appropriate steps in Submit a Requisition as a Subcontractor.