when would be the best time to tell the department for employment in the uk that im leaveing the uk for the usa. i read somewhere that they have to be told just the uk goverment wants to know the ins and outs of a ducks A** anyway

I never told them I was leaving, I don't think they are interested. Remember to claim you taxes back though before you leave, i think its a P85 that you file with the tax office.

Depends you don't have to tell them, I guess you really mean the part that administers benefits and pensions. Then again if you don't tell them you've moved how can they pay any pension you might be entitled to when the time comes.

The best time to tell them is when you leave and have an address in the US you can be contacted at.