Thanks for the clarification, sharonakd. With QuickBooks Online (QBO), each company file is associated with its own separate subscription. I'll give you more information on this.

You can have multiple companies in QBO and each one is required to have their own paid plan. You can access them using the same sign-in information to switch between them easily. 

After you sign up for a QBO plan, import your QuickBooks Desktop (QBDT) company file. For the step-by-step guide, please see this article: Move your QuickBooks Desktop file to QuickBooks Online.

Moreover, after migrating your data from QBDT to QBO, there are tasks you need to complete. For more information on these necessary steps, check out this article: Learn what to do after you move from QuickBooks Desktop to QuickBooks Online.

If you have any other inquiries about subscribing to QBO and migrating your data from QBDT, don't hesitate to comment below. I'm here to ensure that you receive the assistance you need.