PREMIUM subscription is a volume based subscription and works best for accountants having multiple client companies. 

Subscribed users can add upto 30 QuickBooks Companies (30 client companies) at once. More on, adding multiple companies to the app. Now to associate the new QBO company to the PREMIUM plan, each client QB company have to be added to the app with the same userid with which the PREMIUM subscription is purchased.

Each added QuickBooks company in turn can have upto 15 users. More on, adding new users.

You can IMPORT, EXPORT & DELETE unlimited transactions for each QuickBooks Company.

Pricing for PREMIUM subscription: $30.00 /Monthly    $300.00 /Yearly