▁thus ▁reducing ▁tax ▁rates ▁paid ▁by ▁the ▁sp ouse ▁who ▁ear ns ▁more ▁and ▁increasing ▁rates ▁paid ▁by ▁a ▁sp ouse ▁who ▁ear ns ▁less ▁( or ▁nothing ). ▁ ▁Global ▁inc idence ▁and ▁ram ifications ▁for ▁so ver eign ▁deb t ▁and ▁fert ility ▁rates ▁ ▁Most ▁Western ▁countries ▁have ▁abol ished ▁mand atory ▁fict ional ▁income ▁splitting , ▁while ▁in ▁several ▁countries ▁fict ional ▁income ▁splitting ▁is ▁optional ▁( if ▁the ▁couple ▁cho oses ▁it ). ▁A ▁ 2 0 0 9 ▁study ▁of ▁ 2 6 ▁European ▁countries ▁found ▁that : ▁" In ▁France , ▁Lie chten stein , ▁Luxemb ourg ▁and ▁Portugal , ▁cou ples ▁are ▁joint ly ▁ass essed . ▁Ireland ▁and ▁Germany ▁operate ▁joint ▁tax ation , ▁respectively , ▁with ▁an ▁option ▁for ▁individual ▁tax ation ▁and ▁the ▁right ▁to ▁be ▁individually ▁ ▁tax ed ▁when ▁this ▁is ▁more ▁advantage ous ; ▁convers ely ▁individual ▁tax ation ▁is ▁the ▁default ▁option ▁in ▁Spain ▁and ▁Poland , ▁but ▁the ▁option ▁of ▁joint ▁assess ment ▁is ▁offered . ▁Element s ▁of ▁joint ness ▁remain ▁in ▁some ▁income ▁tax ▁codes ▁for ▁which ▁the ▁individual ▁is ▁the ▁unit ▁of ▁tax ation ▁– ▁the ▁Belg ian , ▁Est onian , ▁Greek , ▁I cel and ic ▁and ▁Norwegian ▁codes ▁– ▁some ▁of ▁which ▁are ▁minor ▁while ▁others ▁matter . ▁The ▁remaining ▁countries ▁en force ▁individual ▁income ▁tax ation ▁without ▁exceptions ". ▁ ▁In ▁ 2 0 1 5 , ▁Portugal ▁abol ished ▁the ▁mand atory ▁joint ▁tax ation ▁of ▁a ▁family ,