At this time, QuickBooks Online (QBO) can only handle one company file per subscription. If you have multiple companies, you 'll need to sign up for a new QBO account. This means each company has its subscription. But the good thing is, you can use the same login credentials for all your companies so that the accounts are listed in one place when you log in.
To learn more about creating new companies or switching from one company to the other, check out these articles: