In Chargebee, when consolidated invoicing is enabled, the subscription renewals and unbilled charges for a customer are consolidated into a single invoice. Any 1st invoice raised when a new subscription is created/activated (including those activating after a trial period and those set to start at a future date) is always invoiced separately unless added to unbilled charges.
To avoid a separate 1st invoice, please write to email@example.com to enable the 'Consolidation during subscription activation' feature for your site.
Related articles and Documentation
Why are my invoices not getting consolidated?
How does consolidated invoicing affect my new sales report?