Dealing with the tax authorities can be difficult when arriving new in the Netherlands. They only communicate in Dutch and we have a complicated tax code.
For the year of immigration (also emigration) you need the file the paper M-form for the income tax. Doing this correctly is difficult.
Important item for internationals is the income that is relevant for allowances (zorgtoeslag, huurtoeslag, kind gebonden budget en kinderopvangtoeslag). That is always the worldwide income, even if parts are not taxed here. https://www.belastingdienst.nl/wps/wcm/connect/bldcontenten/belastingdienst/individuals/tax_return/worldwide_income_return/worldwide_income_re_turn/
Contact me if you want to make an appointment.