When you need cash in retirement, you cannot just pull it randomly from whichever account has the highest balance. Every account you own—whether it is a taxable brokerage account, a tax deferred 401(k), or a tax free Roth IRA—has different tax rules.
If you pull from the wrong account at the wrong time, you can accidentally push yourself into a higher tax bracket, trigger taxes on your Social Security benefits, or increase your Medicare premiums. The strategy of deciding which accounts to tap first, second, and third is called withdrawal sequencing, and it is critical to preserving your wealth.