The NCT Number, also called the ClinicalTrials.gov Identifier, is assigned after the protocol information has been Released (submitted) by the Responsible Party and passed review by ClinicalTrials.gov staff. At that time an e-mail notification containing the NCT Number is sent. The record, including its NCT Number, will typically be available on ClinicalTrials.gov within 2–5 business days after it is Released.
See How to Register Your Study for more information.