The answer above applies only to aggregating IRA RMDs and separately to aggregating 403(b) RMDs.
RMDs from other types of plans such as 401(k), 457(b) and the federal TSP plans cannot be aggregated, meaning that RMDs for these other types of plans must be satisfied from the particular plan that has the RMD requirement. RMDs for these other types of plans cannot be satisfied by a distribution from a different account.
Also, RMDs for inherited retirement accounts cannot be aggregated with any RMDs from your own retiremetn accounts.
