Grant Thornton is warning that the new statutory residence test (SRT) which comes into effect this week will have significant implications for UK employers with employees who are globally mobile.

SRT, which applies to individuals for income tax, capital gains tax and inheritance tax, is designed to provide a clear set of rules which supersede all existing residence legislation, case law and guidance.

Tom Richards, tax director in the expatriate employer solutions team at GT, said: 'For employees working full time abroad, there's now a defined amount of time people can spend working in the UK before they become resident for tax purposes - with the threshold set at 30 work days. Previously, there was a lack of clarity in this area.'

Under the new rules, a work day spent in the UK is now defined as any day with more than three hours spent working in the UK, which in some cases will include time spent travelling). 'Incidental' work days - for training or activities subordinate to an employee's main role - will also be included within the 30 day limit.

Richards said employers now needed to track not only time spent by employees on performing their duties, but also travel time for business purposes, which he said represents a new compliance burden.

'If the member of staff goes over a certain threshold, that individual's ties to the UK will come into question and criteria such as whether the individual has an accessible home in the UK, or whether they have a UK resident family, will need to be considered.

'Employers are unlikely to hold this data currently, so one of the major implications of the SRT for employers is an expansion in the amount of information on their employees that they need to gather and keep up to date. The key challenge for business will be developing systems to manage this additional data,' Richards said.