Hi TurboTax! Where do I enter a business expense for the annual fee for Microsoft Online Services (Office 365, eMail, etc)?

The cost of any apps and online tools you use to run your business, such as subscriptions to Adobe Creative Cloud, Evernote, or Dropbox can be claimed under Less common expenses, Office expenses. 

1. On the Tell us about any expenses for XXX screen, scroll down to Less common expenses, Office expenses. Click Continue.
2. On the Let's enter the office expenses for your XXX work, scroll down to enter your subscription amount(s).

[Edited 2-25-18|8:58 am PST]

Assuming this is for a SCH C business.

Under Business Expenses - Other Common Business Expenses you have several places where this could be entered. Pick the one you feel is most appropriate for you.

Office Expenses - You can classify it as such for obvious reasons

Rental Expenses - You are basically "renting" the right to use the software from MicroSoft, since you have to pay for it on a recurring basis, even if that basis is only once a year.

Other Miscellaneous Expenses - If you feel the prior two sections are not appropriate.

The post by @barodius64 is just advertising for a backup solution.