IRA's will often have a death beneficiary, meaning they pass outside of probate. That might be the source of your problem.
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IRS does not control IRA accounts.....the owner controls an IRA account and if the owner/decedent designated who the beneficiary is of such account then you , as executor, can only access the funds if the named beneficiary per bank records is the Estate of the decedent. If any other party is named as beneficiary then you have no authority whatsoever to access such funds. So what are the missing facts here in your scenario?
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To a certain extent, they are right. If there is one or more named beneficiaries surviving, then you as Executor do not have access to the IRAs. Only if the Estate is named or if all of the named beneficiaries have predeceased would you as executor have access to these funds.