The word “aggregate” can be a noun, a verb, or an adjective. In this article, we’re looking at it as a verb. No less authority than Google® defines aggregate as to “form or group into a class or cluster.”
Those who are required to take required minimum distributions (RMDs) from their own Individual Retirement Arrangements (IRAs) are allowed to aggregate their distributions. This allows them, if they choose, to take only one distribution even if they have several IRAs, though it doesn’t preclude them from taking individual RMDs from each IRA.
Let’s say that Joe has four IRAs and is old enough that he is required to take minimum distributions each year (generally age 72 or older). Joe would calculate the RMD from each IRA, dividing the 12/31/2020 balance of the IRA by a factor that is determined by the age he attains in 2021. Tables with the age-based factors can be found in IRS publication 590-B, Distributions from Individual Retirement Arrangements. Joe can then take the RMD amount from one, two, three, or all four of his IRAs. As long as the amount he takes out is equal to the collective RMDs from his IRAs, the IRS doesn’t care from which account(s) if came.
But wait! If Joe also had an IRA that he inherited from his mother, he could not aggregate the RMD from that IRA with RMDs from his own IRAs. If he had two inherited IRAs, both from his mother, he could aggregate their RMDs; but if he had a third inherited IRA (from his father), he could not aggregate that RMD with those from the IRAs he inherited from his mother (and of course he couldn’t aggregate it with his own IRAs).
Roth IRAs do not have required distributions, so aggregating Roth distributions is a moot point. Unless, that is, the Roths are inherited IRAs. Inherited Roths do have required minimum distributions, and the rules in the above paragraph for inherited traditional IRAs apply equally to inherited Roth IRAs.
And don’t even start thinking that you are allowed to aggregate RMDs between your IRA and your spouse’s IRA. The “I” in IRA stands for “individual” and no aggregating of RMDs is allowed, just like the fact that you cannot combine your IRA with anyone else’s.
Aggregating RMDs apply only to IRAs, as described above. Retirement plans, such as the Thrift Savings Plan do not allow aggregation.
Any time an article discusses taxes there are a lot of exceptions, ifs, ands, and buts. When in doubt about the taxability or legality of a particular tax or investment strategy, it pays to do your research and to, if necessary, consult a professional tax or investment advisor.