The IRA aggregation rule was created to limit the ability of taxpayers to take advantage of ‘abusive’ IRA tax strategies, by requiring that all IRAs are aggregated together to determine the tax consequences of a distribution from any of them.
The primary impact of the IRA aggregation rule is to determine how much of an IRA’s non-deductible contributions are treated as an after-tax return of principal when a taxable distribution occurs, whether as a withdrawal or a Roth conversion. And by forcing all accounts to be aggregated together, the rule severely limits many individuals from taking advantage of the so-called “backdoor Roth contribution” strategy.
However, the IRA aggregation rule reaches much further than just the taxability of after-tax contributions in existing IRAs. Thanks to the recent Bobrow case, it now also applies to the limitation of no more than one 60-day rollover in any 12-month period. Though on the plus side, the IRA aggregation rules apply to required minimum distribution (RMD) obligations as well, allowing a distribution from any IRA to satisfy the RMD rules for all IRA accounts!
Fortunately, though, the IRA aggregation rules do not apply when calculating substantially equal periodic payments (SEPP) under Section 72(t), reducing the danger that a withdrawal from one IRA could constitute a “modification” of the ongoing 72(t) distributions from another that would trigger a retroactive penalty. However, even in the case of SEPPs, the IRA aggregation rules will still apply in determining how much of a 72(t) payment constitutes a tax-free return of non-deductible contributions!