Every time you raise an invoice, it is not possible to evaluate the total stock kept on hand. To monitor this, you can set up an alert from within Zoho Books, which will automatically trigger a message once your stock drops below zero.
To set up an Out of stock alert,
Note: The warnings are shown only when you do transactions that affect your stock (either on creating invoice or vendor credit, depending on your mode of stock tracking).
Enabling this option will only display a warning. However, you can still proceed to go ahead with the transaction.
Books
Online accounting software
for small businesses.