This question already has an answer here:
Apologies for the convoluted title - I couldn't think of a better summary.
In the past I did some work for Company A. After I left they were purchased by Company B and completely integrated. Company A simply no longer exists - neither legally nor in name, the team is now simply part of Company B and operate as such. Further, at that point in time I'd never even heard of Company B much less worked with or operated with them.
However, because of my previously relationship with Company A I was asked to come back and work with Company B for a while.
On my CV, it's important to show repeat workplaces because, as a consultant, it shows my reputation and trust. Is it acceptable to simply use the Company B name throughout my CV? I don't want to try and explain the situation on my CV because it takes up space and is easily missed/glossed over - nor do I want to put Company B (Formerly Company A) because that's simply not true.