Hi there.
In QuickBooks Online, each subscription is intended for use with only one company file. Combining different businesses into a single company file can cause significant issues with your company's accounting. However, if you plan on managing multiple businesses with the same Intuit account, you can purchase an additional QuickBooks Online subscription for each separate company.
Moreover, here's an article to learn how to add another subscription to the same account: Create or add another company file to QuickBooks Online.
If you have additional queries about your company file in QuickBooks Online, please don't hesitate to reply below. I'm available to assist you anytime.
