I worked for a company for several years. During my time there, for reasons which I won't go into, my employment switched from Company A to Company B. I was given formal paperwork terminating my employment at A, and starting again at B. Nothing at all changed in my day-to-day employment: same role, same product, same people, same building. The only change was in the legal entity which employed me.
How should I list this on my resume?
Related (but not exactly the same, I don't think): How to list a mashup of employers on resume when working for different companies that are the same company