Is there a functionality or add-on that enables charge accounts, or corporate accounts, where customers are able to charge their orders on the corporate account, and have it billed at the end of the month?
Not really. But what you could do is use Square Invoices to create a work around.
You could:
Create invoice for each customer / corporate account
Add items as they order and then 'save draft'
Keep adding items to that invoice and saving the draft
Send the invoice as a bill once you're ready to (ie at end of the month)
Repeat the above
I would definitely also make sure you've got the customer setup in Square too so you can assign the invoice to them (and then helps with tracking previous orders etc).
