Marital versus Separate Property
As a general rule, the divorce process focuses on splitting marital property, which state law usually defines as all property acquired or earned during the marriage with exceptions typically including inheritance and gift property. Everything else is separate property and not divisible by the court. State law can provide a spouse with the opportunity to trace separate property through a joint account. If your spouse takes money from a joint account and can show deposit slips, bank statements or other records to indicate that monies in the account were his separate property -- such as those obtained through an inheritance or gift -- it's possible that he won't have to reimburse you with all the missing funds.
In the nine community property states, half the money in a joint account belongs to each spouse -- and each spouse is generally entitled to reimbursement of his half as part of the property settlement. If your spouse withdraws money from your joint account, it depends on what he did with the money as to whether he has to pay you back directly or accept a greater share of marital debt than he would otherwise receive. Also, your spouse might have the opportunity to trace separate property through the account, which can mean that he won't owe you half the money that he took from the account.
In the 41 other states, the courts divide marital property and debt under the concept of equitable distribution. In equitable distribution, courts must divide property equitably, or fairly. Because a fair division and an equal division aren't always the same thing, equitable distribution courts can award unequal divisions in the presence of certain statutory factors. Earning capacity, physical and mental health and the size of a party's separate estate are all common factors that can influence a court towards awarding a lopsided distribution. Because of this, the court in your state might not award you or your spouse exactly half of the joint account. Additionally, the court could include the missing cash in the final distribution, treating it as an advance of your spouse's share of the marital estate.
Reasons for Taking Money
Your spouse's motivation for taking the money can become highly relevant when it comes to joint accounts. While courts tend to frown on pre-emptive strikes aimed at leaving the non-withdrawing spouse too broke to hire an attorney, it may find it permissible to "clean out" the account to catch up on past-due marital bills or prevent the repossession of marital property. Other legitimate needs, such as self-support by an unemployed homemaker spouse or hiring an attorney, could affect whether or not the non-withdrawing spouse gets reimbursed.