How many GB does quickbooks need a month

GB? Do you mean data traffic? Any specific concern?

Thanks for posting your concern here in the Community, @Coral01.

I'm here to help you with your concern. 

If you're referring  about the system requirements for your computer’s operating system, your internet speed, and your web and mobile browser vary depending on your system. For optimal QuickBooks Online performance, we recommended the following computer operating systems and internet speeds:

If you're not sure which operating system your computer has, here’s the Windows version page or the Mac version page where you can find out.

• Windows PC: Windows 10, Intel Core i5 or comparable processor (2015 or newer) with at least 4 GB of RAM. Note: You need Adobe Reader 11.0 or higher to print forms.
• Mac: OS X "High Sierra" 10.13 or newer.
• Internet connection: 3 Mbps or higher.

To learn more about this what computer and browser you need for the best QuickBooks experience. Check this article: System requirements for QuickBooks Online

Please update me on how it goes. I'll be right here if you need anything else with QuickBooks. Have a nice day!