I am 90% of the way to being able to completely model our finances where my wife and I split the expenses 50/50 from our own accounts and income. The missing piece is being able to direct income streams to the expenses one person is responsible for. Currently I am directing each person’s salary / pension to a specific account (e.g. my taxable investments), which can be used in the following year. This is very close, but not completely accurate.

An option I think would make it far easier to model similar scenarios (expense payment splits) would be just specifying that the funding of an expense owned by one person come only from accounts and income that person owns. Every expense, income, and account already has an owned by attribute.