If you intend to leave your children equal shares of your estate, don’t forget to consider any money or property held jointly with a child. If you have recently added a child to a bank account, own property jointly with one of your children, or have set up a payable-on-death account with a child as the beneficiary, you might want to revise your will, or at least reconsider how the asset is titled.

Here’s why: Property in a joint account passes outside of your estate. If you add a child to one of your bank accounts, perhaps as a convenience because the child is helping to manage your finances, the account will pass to that child alone when you die. This is true for any property held in joint tenancy, or any property in a payable-on-death account.

If your will says that your estate will be divided equally between your children, then only your other property will be divided equally between them. The child named on the joint account will get all that money or property alone. If you don’t intend for that child to receive a bigger share of your estate, you can add a provision in your estate planning documents stating that any property passing to a beneficiary through joint ownership will be treated as an advance on that beneficiary’s share. In that way, all your children will be treated equally (assuming you have enough assets in addition to the joint property to equalize the shares).

In some states, there’s an additional problem with “payable on death” accounts, which has to do with who pays the estate tax. Consider the case of James Sheppard, a Wisconsin man who died in 2007, leaving an estate of about $12 million. Among Sheppard’s chief assets were two accounts totaling $3.8 million, which were set up so they were “payable on death” to his goddaughter Jessica. After Sheppard died, Jessica received the money.

The $3.8 million in the accounts was counted as part of Sheppard’s estate for purposes of calculating his estate tax. Since the tax was considerable, Sheppard’s executor asked Jessica to contribute her “fair share” toward paying the tax. But Jessica refused. A lawsuit resulted, which went all the way to the Wisconsin Supreme Court.

The result? Jessica won, and didn’t have to contribute a penny toward the estate tax.

In general, the executor of an estate is supposed to pay all the taxes out of the probate assets. Since the “payable on death” accounts were outside of probate, they couldn’t be tapped to pay the taxes.

Now, there are some exceptions to this rule. For instance, in some cases an executor can recoup money to pay estate taxes from a spouse who inherited non-probate assets, or from the beneficiary of a life insurance policy. But Jessica didn’t fall into any of these categories.

Also, some states have their own rules saying that people who receive certain non-probate assets have to contribute to estate taxes. But Wisconsin doesn’t have such a rule, and the court refused to create one.

So in the end, Sheppard’s other heirs bore a disproportionate share of the tax burden … which might not have been what Sheppard intended. The bottom line is that you should always let your estate planner know any time you add someone as a joint owner of an asset or you add a transfer-on-death provision to an account. Otherwise, even though you divided your assets “fairly” in your will, the actual result might be very different from what you intended.