why do we have to change SSN after receive GC?

Can we still use the old one? any other reason to get a new number other than 'for work only'.
thanks！

所有跟帖： 

• I didn't change. It's been 5 yrs. no problem. -金色風鈴- ♀ (0 bytes) () 07/09/2007 postreply 18:53:38

• 不會有新號碼了. -I751- ♂ (86 bytes) () 07/09/2007 postreply 19:00:55

• 回複：why do we have to change SSN after receive GC? -spurs- ♂ (16 bytes) () 07/09/2007 postreply 19:02:17