Updated July 29, 2026. Quick answer: Idaho Code §32-906(1) provides that “the income, including the rents, issues and profits, of all property, separate or community, is community property” unless the conveyance says otherwise or both spouses agree in writing. That makes Idaho an outlier — most community property states treat income from separate property as separate.
The rule, and what it reaches
Bring separately owned property into an Idaho marriage — a rental building, a portfolio inherited before the marriage, a business owned beforehand — and the asset stays separate, but what it earns becomes community property by default.
| What you own | Classification in Idaho |
|---|---|
| Property owned before marriage | Separate |
| Property acquired by gift or inheritance | Separate |
| Rents, issues and profits of that separate property | Community — unless a written agreement says otherwise |
The statute supplies its own opt-out and it is specific. The default is displaced only if the conveyance by which the property was acquired provides otherwise, or both spouses declare by written agreement “specifically so providing.” An informal understanding does not do it, and neither does simply keeping the income in a separate account.
Why the difference is worth knowing rather than trivia. Community property classification decides what happens to basis at the first death — IRC §1014(b)(6) gives BOTH halves a new basis, where a common-law state gives only one. So which assets are classified as community, and from what date, decides how much of that benefit you actually get.
Which cuts both ways here. Income reclassified as community is income that participates in the double step-up at the first death. For a long-held rental generating decades of reinvested income, that is a meaningful benefit rather than a nuisance — provided you know it happened.
Sources
Each state’s own codified statute as quoted on this page. The nine-state list and the federal treatment are per IRS Publication 555 and Internal Revenue Manual 25.18.1.2.3. IRC §1014(b)(6) for the basis consequence. All read July 2026.
This states what the cited authority says. It is not tax advice, and retirement-plan design turns on facts about your business and your other entities that no page can see. Every dollar limit referenced here is indexed and changes annually.