I have a fashion truck, and online store; the majority of transactions are made via invoices.  My VA and I have been inadvertently overselling items.  Is there a way to track items (in real time) that are in stock?  
When I spoke with an account rep, she indicated that items that were sold through an API/square online store and register were tracked in real time - however, we were still able to oversell items. I can somewhat understand that an item could be oversold via invoice (but not if the same description was used). Have you bootstrapped anything together to make it work?

Is there an inventory management app that would help with this?  Which do you recommend, or recommend NOT using?

And, have barcode scanners helped  with managment? 

I'm feeling like I've outgrown Square 😞 😞