Will your Last Will and Testament that you've written in your former state of residence still work after you move to a new state? Like many aspects of estate planning, the answer to this question is, "it depends."
Was Your Will Valid in Your Former State?
If your will was created and signed with the proper formalities as required by the laws of your former state of residence and was considered a valid will there, then it should still be considered a valid in your new state. But if your will was not created and signed with the proper formalities in your former state, then it will not be valid in your new state.
For example, if the laws of your former state require a will to be signed in front of three witnesses but you only signed your will in front of two witnesses, then since your will was not valid to begin with in your former state it cannot possibly be valid in your new state.
Aside from this, some states recognize "nuncupative wills" and/or "holographic wills," while other states do not recognize these types of wills. A nuncupative will is a verbal will that is spoken in front of two or more witnesses, while a holographic will is one that is written entirely in the Testator's own handwriting and signed and dated by the Testator. If you make a nuncupative will or holographic will that is valid in your former state but your new state does not recognize this type of will, then your will will not be valid in your new state.
Other Problems to Consider
While your will may still be valid after you move to a new state, certain parts of it may become invalid or may require changes due to the unique laws of your new state.
For example, in Florida your Personal Representative must be related to you by blood or a certain degree of marriage, a Florida resident if not your relative, or a bank or trust company with power to act as a fiduciary in Florida. Thus, if you are an Illinois resident and you make a valid will while living in Illinois and name your best friend who is also an Illinois resident as your Personal Representative and then you move to Florida, your best friend will not be allowed to serve as your Florida Personal Representative.
What You Should Do
If you move to a new state, sit down with an estate planning attorney who is familiar with the probate, trust and estate tax laws of your new state. This will insure that your estate plan will continue to work the way you expected it to work in your old state.