因此, 以你的情况, 若要退税, 就不能在此停留STAY超过三年, 哪怕是多一天(若是三年为限). 若是两年为限, 就不说了.
[http://www.hmrc.gov.uk/pdfs/ir20.htm#double]
Teachers and researchers
9.7 Under some agreements, if you are a teacher or professor who comes to the UK to teach in a school, college, university or other educational establishment for a period of two years or less, you are exempt from UK tax on your earnings from the teaching post. Temporary absences from the UK during this period normally count as part of the two years.
Some agreements cover persons who engage in research. Where this is so, the rules are normally the same as for teachers.
9.8 If you stay for more than two years you cannot claim exemption and you will be liable to tax on the whole of your earnings from the date you arrived. Some agreements only allow exemptions to be given if the earnings are liable to tax in your home country. If you have already received exemption for a visit (or visits) of up to two years, some agreements will not allow you to claim the exemption again if you make a further visit at a later date.