What licences are required?

Patrick,

There is no specific license required for a general tech support company. Typically, you would just need to have the company registered with the state you are conducting business in, and obtain a federal tax id (EIN).

Depending on your residency, and if this would be a web-only business, you may want to consider registering in business-friendly states such as Wyoming or Delaware, as these are very common states for your type of business.