Marital property is generally everything either spouse acquired during the marriage, regardless of whose name is on it. The paycheck, the house, the retirement contributions, the car, the furniture, the debts. Whose name is on the title usually does not decide it.
Separate property is generally:
A minority of states — Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington and Wisconsin, with Alaska offering it by election — treat marital property as owned equally by both spouses. The default is a 50/50 division.
This is simpler but less flexible. The split is on the value of the whole pot, not item by item: one spouse can keep the house and the other receive assets of equal value.
Every other state divides marital property in a way the court considers fair, which is not the same as equal. Judges weigh factors that commonly include:
In practice equitable distribution in a long marriage often lands near equal. In a short marriage, or where one spouse brought substantially more in, it may not.
This is where most of the real money is decided, and it catches people out constantly.
Separate property mixed with marital property can lose its separate character. An inheritance deposited into a joint account and used for household expenses is the classic example. Depending on the state and how thoroughly it was mixed, it may become entirely marital.
If a separate asset grows in value because of work either spouse did during the marriage, the increase is often marital even though the asset is not. A business owned before the marriage that one spouse then ran for fifteen years is the common case.
Passive growth — a share portfolio that simply rose — is more often treated as remaining separate, though states differ.
Paying the mortgage on a pre-marital house out of joint income, or renovating it with marital funds, usually gives the marital estate a claim on part of its value.
Adding your spouse to the deed of a house you owned before the marriage is frequently treated as a gift to the marriage, converting the whole thing.
If you want to keep something separate, you have to be able to show where it came from and that it stayed apart. That means documents: the account statement showing the inheritance arriving, the statements showing it was never mixed, the pre-marriage valuation of the asset.
The burden is generally on the person claiming an asset is separate. Without records, a court may simply treat it as marital. This is the single strongest argument for keeping inherited and pre-marital money in its own account.
Unlike support and parenting arrangements, which can be modified when circumstances change, the division of property is usually permanent. It can only be reopened in narrow circumstances — typically fraud or concealment.
That asymmetry is worth holding on to while you are negotiating. A support figure that turns out to be wrong can be revisited. A property split that turns out to be wrong usually cannot.
Warning: This post is neither financial, health, legal, or personal advice nor a substitute for the advice offered by a professional. These are serious matters, and the help of a professional is recommended as it can impact your future.