I really don't know what y'all do over there but here you take the commercial written for the commercial, the instrument written for an IR and an ATP written for an ATP. Seems simple, right?
Tinstaafl is right, you don't need an instructor sign off for the ATP written or checkride. The FAA figures by the time you get to the ATP level you should know when you are ready. But now you need an ATP CTP completion certificate to take the written. And if you are getting a type rating as part of the ATP there has to be a record of training.
For the IR and commercial you are going to need an instructor's signoff for the written and checkride. Some of the online training programs will issue a course completion certificate that will count as a signoff for the written.