Understanding Service Credits under 99.9% Service Level Agreements (SLA)

The new Microsoft Online services represent an excellent option for businesses to base all or part of their Exchange, Sharepoint and MeetingPlace functionality within a Microsoft hosted data center.

But what about Service Level agreements for these services. What happens, for instance, if the service goes down for 2 hours in the middle of the day?

The following documents:

Microsoft Exchange Online Service Level Agreement

Microsoft Sharepoint Online Service Level Agreement

Microsoft Office LiveMeeting Service Level Agreement

are all quite similar and outline the Service Levels guaranteed by Microsoft for availablity, but with some important conditions and exclusions which need to be understood.

For instance, Microsoft offers "Service Credits" if the service is not available for a certain amount of time. These credits are based on the following table:


Monthly Uptime Percentage

Service Credit

< 99.9%


< 99%


< 95%


At first glance, it looks as if almost any disruption in service would result in a refund from Microsoft. In calculating "Monthly Uptime Percentage" however, Microsoft uses the following formula:

TM = Total Number of Minutes in a Month

TU = Total Number of Users

Monthly Uptime Percentage = (TM*TU-Total minutes of downtime for all users in the month)/ (TM*TU)

As a result, if I have 40 users in my organization, and one of them experiences some kind of outage for 2 hours in December, the Total Uptime Percentage would be calculated as follows:

Total Uptime Percentage = (44640*40-120)/(44640*40) = 0.99993279569892473118279569892473

As a result, a Service Credit would not apply.

If, however, all 40 of those same employees experienced outages for 2 days during the same time period, the Total Uptime Percentage would be

Total Uptime Percentage = ((44640*40)-(2880*40))/(44640*40)=0.93548387096774193548387096774194

At first glance, it would seem as if a 100% Service Credit was due, however a careful look at the SLA shows other caveats. First, the SLA does not apply to any performance or availability issues:

  1. Due to factors outside Microsoft reasonable control

  2. That resulted from Customer's or third party hardware or software

  3. That resulted from actions or inactions of Customer or third parties

  4. Caused by Customer's user of the Service after Microsoft advised Customer to modify its use of the Service, if Customer did not modified its use ad advised

  5. During beta and trial services (as determined by Microsoft)

and finally,Service Credits are only provided if the customer has submitted an incident to Microsoft support services and filed a special claim for credit within 5 days of the initial incident.











Skip to main content