IRA distributions made to IRA owners before they reach age 59 1/2 are generally subject to an extra 10% penalty in addition to regular income tax. There are about a dozen exceptions to the tax (distributions that can be taken penalty-free). The most popular for planning purposes is the "series of substantially equal payments" (SOSEPP). If IRA owners design their "series" of payments in accordance with strict IRS rules, and keep taking their series payments regularly without any "modification" until they are over age 59 1/2 (and for at least five years), the SOSEPP payments are penalty-free.
IRS rules offer three methods of designing the SOSEPP (annuitization, amortization, minimum distribution), a choice of interest rates (anything up to 120% of the applicable federal rate), and a choice of life-expectancies over which the series payments will be computed (single, joint with beneficiary, or Uniform Table). (The series is computed based on the assumption of a lifelong payout, even though payments can be discontinued once the age 59 1/2/five-year requirement is met.)