What are non-resident claims?
A Non-Residency claim is one in which a Seafarer does not spend more than an average of 90 days per annum in the UK. (Please note spending less than 90 days in the UK does not guarantee a claim to Non-Residency as there are many more factors involved.)
The non-resident claim must extend over at least one complete income tax year, ie 6th April to 5th April the following year.
The above is only a broad outline, as there are further rules that apply to non-residency tax claims.
It is also very important to note that any earnings relating to duties earned whilst in the UK continental shelf may be taxable regardless depending on what sort of vessel you work on. i.e it does not depend on residency.