as previously mentioned:
AIP ENR 1.10-6, paragraph 2.20.
Review the table for your answer.
'FULL FLIGHT DETAILS' refers to the NAIPS 'ICAO' flight notification
'SARTIME' refers to the NAIPS 'SARTIME' flight notification, a cut-down and simplified version of the ICAO flight notification.
'FLIGHT NOTE' refers to leaving a note with a responsible person to follow up your safe arrival. Read family / friend / colleague.
As the table states, FULL FLIGHT DETAILS are required for all IFR flights and VFR into CTA. CTA does not include a Class-D CTR from Class-G. The final row of the table specifies the flights that require NO NOTIFICATION whatsoever.
This could be confirmed by an ATC guy, but if you turn up unannounced at a CTA boundary asking for a clearance, you are simply asking the controller to undertake the least preferred method of flight notification submission. That is, a last minute submission over the radio, where a controller has to make your flight plan on the spot, when you could/should have done it yourself prior to flight. You're entering CTA as per ENR 1.10, but the controller had to make the 'FULL FLIGHT DETAILS' notification on your behalf....