The FI Tax Year runs from 1 January to 31 December. If you receive income from property or land regardless of where it is situated, you are required to included this in your tax return.
If you have property in the Islands but do not reside here, this still needs to be declared in your return, no matter what your tax residency status is.
FI has its own taxes legislation and any deductions given by non-FI authorities do not apply when calculating income for FI tax purposes.
For further information on what you expenses you can claim against rental income, please see the relevant guide:
Residential Letting In FI
Residential Letting Outside FI
Non Residential Letting Outside FI