CAC stands for Corporate Affairs Commission. This is the Nigerian body saddled with the responsibility of registering any new company in Nigeria. They have wide spread reach all over Nigeria. 
You will find their office in virtually all states of the federation, including the federal capital territory. If you need to register any company, you must locate them to get things done. You can visit their headquarters in Abuja or visit any of their state offices. In order to learn more about them, you can pay their website a visit.
Corporate headquarters
Their corporate headquarters is located at Abuja as hinted earlier. They can be found at Plot 240, Tigris Crescent, Off Aguiyi Ironsi Street, Maitama, Abuja, Nigeria. The state offices can handle certain company registration issues, but there are some other specific ones that must be referred to the head office for proper handling. They may therefore refer you from the state office to the Abuja office at times.
Telephone lines
You can call any of their customer care lines for any information whatsoever. The customer care lines are: +2348182299016 and +2348182298971. You can call their Public Affairs agents on +2348097388192.
Postal address
In the event you prefer to contact them via post office, you can mail them on P.M.B. 198, Garki, Abuja, Nigeria. This will take longer to reach them compared with when you contact them via phone call.
Their official website
The corporate affairs commission can be reached via http://new.cac.gov.ng/home/. You can learn everything you need to know about their activities on their website and even register your company on the website.