Just because you have a will doesn’t mean your work is done. A jointly held account, for instance a bank account, passes by title, not will. If, for example, you and your spouse have a joint savings account, it will pass to the surviving spouse. That happens, not because your will says you want everything to go to your spouse, but because that’s how the account is titled. That’s a simple example, and one where things happened to turn out okay. But, let’s look at another case: