How do Rule 72(t) / SEPP withdrawals work for early retirement?

Rule 72(t) lets you take penalty-free withdrawals from an IRA before 59½ if you commit to "substantially equal periodic payments" (SEPP) calculated by one of three IRS-approved methods. The catch is rigidity: once you start, you must continue the same payment schedule for at least five years or until you turn 59½, whichever is longer. Change or stop early — or take an extra withdrawal — and the IRS retroactively assesses the 10% penalty on every distribution plus interest. The amount is set by your account balance, your age, and a reasonable interest rate, so it isn't flexible if your spending changes. Many FIRE planners split a single IRA into a smaller "SEPP IRA" sized to the income they need, leaving the rest untouched. Because the lock-in is unforgiving, run the numbers carefully and consider pairing 72(t) with a cash buffer for surprises.