I can't normalize these tables

[Farhan Qazi]

I am in the process of normalization of my database which deals with clients information. I have made one table for clients information in which `client id` is Primary Key.
The problem is that the clients can have either A type of company or B type of company and depending on the TYPE of company, the details needed will be changed like if A type of company then only name should be stored, and if B type of company then name, registration date, accounts info should be stored.
I thought that i should use the PRIMARY KEY of CLIENTS table 'client id' as the PRIMARY key for the A type table and B type table, hence using the same PRIMARY KEY in three tables to relate the data to the same client.
Please advise me what is the best way to achieve best normalization.