When Do You Need a Will? When do you need a will? The answer is easy: Right Now. Share | Related Content When Special Care Is Needed: The Special Needs Trust A special needs trust helps care for a special needs child when you’re gone. Put It in a Letter A letter of instruction provides additional and more personal information regarding your estate. What Is My Life Expectancy? Estimate how many years you may need retirement assets or how long to provide income to a surviving spouse or children.