In order to determine your balance as of December 31 of the previous year, you aggregate accounts of the same type:
IRAs, SEP-IRAs, and SIMPLE IRAs get aggregated.
Note that inherited IRAs do not get included here—they have their own category and only inherited IRAs from the same decedent can be aggregated. Additionally, if you have named a spouse as the sole beneficiary on any IRA and the spouse is more than 10 years younger, you must calculate the distribution on that account separately.
You can aggregate together all 403(b) accounts as you do with IRAs.
Once you total the balance from the category and calculate
the distribution, you are permitted to take the distribution from any
one or all of the accounts in that category.
Qualified plans (Keogh, 401(k)) cannot be aggregated, and the minimum distribution must be calculated and distributed from each plan.