Assets that are co-owned with someone else, or which are titled payable on death to a designated beneficiary, are not governed by the terms of the Will. These assets pass by operation of law, outside of the Will. This is an important distinction.
For example, let’s say your Will states that your assets are to be divided equally between your son and daughter. Let’s further assume that you have named your daughter as a joint tenant on your bank account because she lives nearby. That account contains the bulk of your assets. Upon your death, the assets in that account will pass entirely to your daughter, by operation of law. The fact that your Will states that assets are to be split fifty-fifty is irrelevant with respect to that asset. How will your daughter and son handle this? Will your son be angry? Will be and your daughter works things out, or will this harm their relationship?
This example highlights one of the problems with maintaining joint accounts: It is difficult to continuously calibrate what is in each brokerage, bank and checking account. It is far easier to have these assets pass under your Will. If you have assets that are co-owned or have a designated beneficiary, it’s important to keep those designations up to date, and make sure they are consistent with the terms of your Will.