TSEM9812 | Property held jointly by married couples or civil partners: Overview: two main rules
From HM Revenue & Customs · Trusts, Settlements and Estates Manual
There are two rules about property held jointly by married couples and civil partners:
the ‘50/50 rule’ (ITA/S836) whereby most income from jointly held property is treated as split equally between the two spouses or civil partners for income tax purposes; the 50/50 rule applies unless there is a valid declaration on form 17; sections TSEM9814-9840 contain the details;
the ‘form 17 rule’, whereby, if the true income split is different from 50/50, the couple can opt to be taxed on that basis for income tax purposes (ITA/S837); sections TSEM9842-9878 contain the details.