A statement is a concise summary of outstanding invoices that you send to a client in order to chase up payment or to provide confirmation of payment. While this can be done at any time, it's probably worth ensuring your bank reconciliation is up to date so that you have accounted for any recent payments made that should be accounted for before sending the statement.
In certain instances, the Accounts Payable department may even request a statement directly to reconcile their accounts. Regardless of the intended purpose, a statement is prepared and ready for distribution at any time.