Is my spouse entitled to half my 401(k)?
Generally your spouse has a claim on the portion that accrued during the marriage, not on the whole account and not automatically on half of it. What you had on the wedding day, and what accrues after the marriage ends, is usually treated as separate.
This was the single most repeated question across everything we mined, from both directions, and the answer is less alarming than the search results suggest.
How it actually works
Take a retirement account you have paid into for twenty-five years, ten of them married. Broadly, the ten married years are marital property and the fifteen are not, so in most states only the marital portion enters the pool. A few states are the exception and can divide everything regardless of when it was earned: Washington, Indiana, Massachusetts, Connecticut, New Hampshire and Vermont are the usual examples, and the list is not a closed one, so check your own state rather than assuming it is not on it.
What happens to that portion depends on where you live. In the nine community property states the marital share is usually split equally, though the nine are not uniform: California directs an equal division, Nevada directs one only so far as it is practicable and lets a judge split unevenly for a compelling reason stated in writing, and Texas and Washington divide on a just and equitable standard where uneven splits are ordinary. Everywhere else it is divided fairly, which may or may not be half.
And the division happens across your whole estate rather than account by account. A spouse entitled to value from your retirement might take the house equity instead, and everyone walks away balanced. Retirement is not special in that arithmetic; it is just usually the largest number.
Whose name is on it does not matter. This is the part people find hardest to accept. A 401(k) in your name, funded by your salary, is still marital to the extent it grew during the marriage, because the salary was marital too.
Different accounts, different machinery
401(k)s and pensions need a separate court order, a QDRO, before the plan will move anything. The decree alone does not do it, and the order that never gets filed is a genuine and expensive problem.
IRAs divide through a different mechanism, without a QDRO, and the difference is not only paperwork. The exception to the 10% early-withdrawal penalty applies to employer plans only; there is no equivalent for IRAs. If you need to spend any of what you receive before 59½, taking it under the QDRO rather than after it has rolled into an IRA can be the difference between a penalty and none. Ask before the money moves.
An IRA also has to wait for the judge. The tax-free split only works off a decree, or a document the decree takes in, so dividing an IRA on a signed settlement agreement before anything reaches a judge is treated as you withdrawing the money: tax, plus the penalty if you are under 59½, on cash that has already gone to your spouse. Never withdraw and hand it over. Move it custodian to custodian once the decree is signed.
Government and military systems have their own procedures again.
Done correctly, a transfer between spouses as part of a divorce is generally not a taxable event and does not trigger early withdrawal penalties. Done incorrectly, it can be both, which is the reason not to improvise this.
The three things not to do
If you are not safe, this section does not apply to you in the same way. Federal law allows a penalty-free withdrawal, up to $10,000 or half the account, whichever is less, for someone experiencing domestic abuse by a spouse or partner, and the timing of any financial move deserves an advocate's help first. Two limits are worth knowing now rather than later: it has to be taken within a year of the abuse, so it is not there for you several years on, and it comes from an IRA or most 401(k)s, not from a pension. If an employer plan says it does not offer this, that is allowed, and you have not lost it. You can still take a withdrawal the plan does permit and claim the exception on your tax return. An IRA needs nobody's permission at all. The safety resources page has the numbers, free and confidential at any hour.
Do not empty it. This is the instinct behind half the searches on this topic and it is the worst available move. You will trigger taxes and likely a penalty, the money is still traceable and still marital, and a court can simply credit the whole withdrawal against your share. You will have paid a substantial fee for the privilege of losing the argument anyway.
Do not stop contributing without advice. Halting contributions the month things get difficult looks like managing the number, and the reduction usually hurts you more than your spouse in the long run.
Do not take a loan against it to fund anything related to the divorce. It creates a marital debt against a marital asset and complicates the division you were trying to influence.
What to do instead
Get the numbers. Statements from the wedding date and from now. The marital portion is a calculation, not an assertion, and for pensions it usually needs an actuary.
Do not forget survivor benefits on a pension. They are separate from the division itself and they are a classic thing left out of a decree, discovered years later when they cannot be fixed. Divorce ends the protection a spouse has automatically, so the order has to name survivor benefits in so many words. An order that splits the monthly payment but says nothing about survivor benefits looks perfectly correct, and your share simply stops the day your ex dies.
Think in after-tax terms. A dollar in a traditional retirement account is worth less than a dollar in savings, because tax is waiting on it. Trading one for the other at face value is a real and common mistake.
Confirm the transfer actually happened. The most expensive failure in this area is not an unfair split. It is a fair one that nobody carried out.
How the marital portion is calculated, and how it is then divided, are state law; the mechanics of moving money out of an employer plan are federal. Both matter here, and a botched retirement division is difficult to undo, so this is a good use of a professional.