Although the RMD amounts are calculated separately for each IRA plan, once calculated, you can distribute the entire required amount from any account in any of your IRA plans (excluding Roth IRA, Inherited IRA, and Inherited Roth IRA plans) at any financial institution.
You can also withdraw a portion from each IRA plan
Withdrawals from a non-IRA plan, such as 401(a) or 403(b), cannot be used to meet the RMD requirements for your IRA and vice versa.
RMDs have to be calculated and distributed separately from each plan for the following plan types:
Inherited IRA
Roth Inherited IRA
401(a) plans such as profit sharing or money purchase
403(b) plans such as Tax-Sheltered Annuity or Tax-Sheltered Custodial Account