Of course I don't know all of Yangwha's details but in my case I was on the UK payroll, despite being deemed out of the country sufficiently long enough to get a tax rebate. So in my case payslips and a P60 wouldn't really give any detail of my whereabouts. Passport stamps did, however and these were used to help prove my absence from the UK. ( I had to go out of my way to make sure I got my passport stamped every time I arrived in another country. )