If I have a job in the UK, with a UK company, where I mainly work from home using the internet, what would happen if I were to do it a lot of the time in the US? Assuming that the company don't care where I work as long as I get it done.
Is there a minimum amount of time I would need to spend in the UK? Is there a maximum amount of time I am allowed to spend in the US (at a time or total per year)?
I know that under the visa waiver scheme I have to have a return ticket bought and I can stay no longer than 90 days, but is there anything to stop me going for 80 days, coming back for 10 days, and going out again?
The leaving the US for a few days no longer works now. If you were to go back for a few days they'd not likely let you in again for a while. You'd also need a VISA as you'd be there on business. A long business visa is unlikley to be granted without a company sponsoring you or details of where you're going to be working.
As for UK tax you need to spend 183 days in the UK to be though of as a UK tax resident. However this drops to 91 days over a 4 year period.