Transfer a job from one active company to another active company

I need to transfer a job from one active company to another active company.  Some of the costs occurred in prior years.  I've gone through the knowledge base but cannot find anything specifically relating to transferring from one active company to another active company. It discussing how to move in or out of an archieve file.  I may be using the wrong terminology to extract the informaiton I am looking for.  Can anyone walk me through or point me in the right direction?