Jason Porter of expat financial advisory firm Blevins Franks answered this question.

“Basically, if you spend more than 183 days in the UK in a tax year (6 April 6 to 5 April), then you are tax resident in the UK. The number of days falls depending upon the number of ties with the UK. The ties are:

• Family members in the UK (for example a spouse or children)
• Accommodation, that is a place to stay which is available to you for a continuous period of 91 days (thus excluding hotels)
• 40 working days of three-plus hours per day or more in the UK
• More than 90 days spent in the UK in at least one of the previous two tax years
• You have spent more days in the UK than in any other country during the tax year.

“Understanding how many ties which are required to determine your residence status will depend on the number of days you spent in the UK during the tax year:

[one_half]Days spent in the UK in the tax year under consideration

16-45

46-90

91-120

Over 120      [/one_half] [one_half_last]UK ties needed to be considered a UK resident

At least four

At least three

At least two

At least one[/one_half_last]

This link is to the taxman’s own document on the subject:

https://www.gov.uk/government/uploads/system/uploads/

attachment_data/file/547118/160803_RDR3_August2016_v2_0final_078500.pdf

“The tax guidance says that days spent in the UK may be ignored if the individual’s presence in the UK is due to exceptional circumstances beyond their control. These circumstances could include civil unrest, natural disasters, outbreak of war, sudden serious or life threatening illness to the individual, their spouse, children or cohabitees.
 
“The guidance does not include parents, so you may have to depend upon day-counting.”