How to know which contacts have time to be invoiced?

How to know which contacts have time to be invoiced?

Just moved from QB to Zoho Books and now working on using the integration between Desk and Books...

I see that if we go to a contact, we can see time and generate an invoice from that screen. That looks slick. 

Question: How do I know which contacts have billable time in the first place? We have hundreds of contacts and it would be helpful to be able to see just a list of contacts with billable time. Even better would be to see a consolidated list of time that is billable (and generate invoices from that screen). 

Thanks,

Scott