Considering that these services are able to properly validate a phone number in real time, even if the information comes in a bulk, the process is based on multiple steps that must be respected and individually fulfilled in order to appropriately deliver a result. The first part of the operation is the format checking. The program will verify if the structure of the phone number follows the appropriate format for the region it originates from. Everything from number of digits and country codes to special characters gets to be analysed before issuing the result: if a number is improperly formatted, the information gets automatically flagged as invalid.