Tier 3
  

Expert product and service support
  

Access to the highest technical resources available for problem resolution or new feature creation.

Tier 3 technicians attempt to duplicate problems and define root causes, using product designs, code, or specifications.

Once a cause is identified, the company decides whether to create a new fix, depending on the cause of the problem. New fixes are documented for use by Tier 1 and Tier 2 personnel.
  

Tier 3 specialists are generally the most highly skilled product specialists, and may include the creators, chief architects, or engineers who created the product or service.

Tier 4
  

Outside support for problems not supported by the organization
  

Contracted support for items provided by but not directly serviced by the organization, including printer support, vendor software support, machine maintenance, depot support, and other outsourced services.

Problems or requests are forwarded to tier 4 support and monitored by the organization for implementation.