I will throw this into the mix. When I sold my business I was asked for the the past employees liability insurance documents, I had kept the last 16 years worth of them. I think they have to be kept for 40 years.
Also I employed a guy as a contractor for about nine months and was told that if the guy was working solely for me for more that about two months then the I.R. would treat that as being an employee in the full sense of the meaning.
I am glad that I am now out of the rat race. Best on luck though. ..Clive