All SharePoint Online plans provide the ability to add additional storage. In the Small Business plans this can be a little hard to locate. Here’s a quick overview of what you need to do.
Login to your Office 365 tenant as an administrator and select Manage and purchase licenses from under the licenses heading at the bottom of the page.
Click on purchase services at the top of the page and then Add under your Small Business plan on the right under the price.
Select optional add-ons item under user license at $XX.XX
Add your storage and complete the purchase.
Now you should be able to assign additional storage to your SharePoint Online site in the Small Business plans.
Adding space is slightly different for M and E plans and I’ll cover that in an upcoming post. Also, the story is a little different for plan in Australia so beware.