income tax

dear Sir,

at my work, I came across self-assessment and income tax computation

the person is from the EU Germany and is a UK residence, now he should be taxed on his worldwide income.

he has a house in the Norway which he rents out and incurred tax at source for the Norway tax authority
other income from Germany
income from the UK.

i contacted HMRC they said the rental income is exempt but did not know why as i am not fully in charge on this self-assessment the question is why the rental income from the house is exempt and how to present the employment income from outside the UK is it same role the income fro the UK,

Kind regards