Welcome to the community family! I'm glad to hear you're using QuickBooks Online to easily manage your business. I'd be happy to share more about this.
QuickBooks Online Plus has several advanced features such as Location and Class to help you track different regions or departments of your company. It's important to note, however, that the sales tax centre is designed to track one business. If you have companies with two different tax numbers, you'd have to use separate accounts for proper sales tax reporting.
I hope this helps to clarify things for you. Don't hesitate to reach back if you have more questions.
One QBO account is for one company file. Should you need to manage branches/divisions, you may utilize the Class and/or Location feature available in QBO Plus. Otherwise you should purchase additional QBO account.