Your distributors track your sales, this includes people like CD baby etc...you need a barcode to be sold in places like amazon and itunes, but again all the shops collate the sales and send them to the distributors. TO actually even print a cd you need to submitt a request to your local mechanical copywrite agency (in the UK it is call MCPS) they check to see if the stuff you are selling is copywrite controlled - if it is notm you will gt a "certificate of no claim" which they forward on to your pressing company, meaning it is legal for you to sell it... You dont need to be registered as a company or ought to start with (these organisations are called IMPRINTS) you can just sell it and be happy....
Any more stuff you need to know, just ask, i have litwerally just been through all of this...
Safe Al