The internet giant is no longer offering products including Gmail and Google Drive for free to companies with 10 employees or less as part of a strategy to increase revenue outside of its search monopoly.
Google will charge the firm's £33 per month to use its web apps, but insists that profits will be used to serve its users more effectively, offering features such as around-the-clock support and larger inboxes.
Individual Google Apps users and existing business customers will not be affected by the change.
Launched in 2006 to offer an online alternative to Microsoft's Office software, Google Apps is used by more than 5 million businesses worldwide, but virtually all of the firm's $38bn annual income is derived from online advertising.
Microsoft continues to add online features to its productivity software in response to the success of Google's services.