How to Use the Spousal Home Ownership Basis Calculator
Korea's comprehensive property tax is charged per person, so married couples compare sole versus joint title mainly to optimize an annual net-worth-style tax bill. The US has no equivalent annual net-worth property tax — ordinary property tax is billed per property based on assessed value, and splitting title between spouses doesn't change that bill at all.
For US married couples, the ownership-structure decision that actually matters shows up later, at the first spouse's death, in two places: stepped-up basis and estate tax portability. In community-property states, the entire value of a jointly owned home gets a full step-up in basis when the first spouse dies — erasing all prior unrealized capital gains. In non-community-property states, jointly held property (joint tenancy) usually only gets a step-up on the deceased spouse's half, leaving the surviving spouse's half at its original basis. And separately, any unused federal estate tax exemption from the first spouse to die can be "ported" to the survivor, who then has both exemptions available (roughly $30 million combined as of 2026) for the remainder of their life.
Enter the home's original cost basis, its fair market value when the first spouse passed, and the ownership type to see how much of the accumulated gain gets stepped up and the capital gains tax that step-up effectively avoids. This calculator isn't a 1:1 substitute for Korea's comparison — there is no annual tax savings being compared — but it captures the real, quantifiable US benefit tied to how a married couple holds title.
Frequently Asked Questions
No. Ordinary US property tax is billed per property based on assessed value, not per owner, so splitting title between spouses doesn't reduce it. The real ownership-structure decision in the US affects capital gains basis and estate tax portability instead.
When one spouse dies, their unused federal estate tax exemption can be transferred ("ported") to the surviving spouse, who can then use both exemptions — roughly $30 million combined as of 2026 — when they eventually pass assets to heirs.