I sold up and moved to Ireland 3 years ago. When I handed my work over, I wrote up a contract, stating what I was selling, how much I was selling it for, and included the terms that I was relinquishing all responsibility for the business, and that the buyer was assuming said reponsibility. I handed over all the customer addresses and prices at the same time, having previously emailed the buyer a summary of the number of customers, locations, frequencies and turnover.
I made up 2 copies of the contract, both parties signed both copies in each other's presence, and the monies were transferred into my bank in my presence.
I then hand delivered a letter to every customer explaining the handover.
Job done. No room for misunderstandings, and the transactions (I sold the business in 3 stages to the same buyer) went ahead without any problems whatsoever.
HTH.
John