eb1(c)...485 self filing


Can i file my eb1(c) multi national manager I140 with my employer but later upon 140 approval...file the i485 by myself i.e. not file my 485 by my employer though i will continue to work with the same employer ?

Will there be any issues in this ? If it will not be any problem then What sort of documents would i still need from my employer ?
My employer is a large mnc.