Can the one QB file be accessed by two computers simultaneously? I want a client and I to access the same file open my computer and on the client computer

I'm glad to assist you, jarpac, 

With Quickbooks Online, multiple users can access the same file at the same time in separate computers. You can access the account as long as you have a stable internet connection to do your work and any changes made are save when you click on the Save button. 

Don't hesitate to post again with any questions. 

Nona