In YE 31 the Yamatai Star Empire started requiring registration and assignment of IRN to its non-military vessels. IRN are numerical designations originally used by the Star Army of Yamatai to identify particular starships. The civilian format is similar to that used by military vessels, but uses ship class instead of fleet.
Y<designation>-C<# of ship class in that type>-<hull number>.
M = Merchant 1 = First class of ship in the category. 0001 - hull number.
Science vessel, first in class, hull 0025
|YK||Star Fortress||Iori, Zodiac|
|YL||Logistics||(has the most ship classes)|
|YM||Merchant, freighter||Odori, Geshrinari|
|YR||Repair Ship||(used by some fleets for Anri DSRs)|
|YS||Scout Ship||Yui, Nozomi|
|YX||Exploration , science|
|YY||Yacht||Type 30 Space Yacht|
Registration for corporation and privately owned vessels is not compulsory. However the Yamatai government encourages registration. By Registering their vessels, they get the benefit of faster response in emergencies, since responding vessels would be able to quickly identify the type of ship from the registration.
C - Corporate owned
P - Private owned
They use the same format as the governmental vessels.
C<designation>-C<# of ship class in that type>-<hull number>.
P<designation>-C<# of ship class in that type>-<hull number>.