Accounting > Billings > Trial Balance Summary
Through the trial balance summary screen, after locating all the outstanding invoices using the report type filter of "Billed and Unpaid", tick which clients you want to send a statement of outstanding invoices to. The Tag/Untag All button will tick all clients.
Click the "Statements" button on the action bar to send statements.
IMPORTANT: Statements will be sent according to each clients invoice dispatch settings. If a client is setup to dispatch invoices to the screen, the statement will be emailed to the user running the statement process