You can provide a qualified disclaimer to the plan administrator of the 403(b). This will make the contingent beneficiary, the beneficiary of the account, as if he were the primary beneficiary, and the primary beneficary will be treated as if he had predeceased the retirement account participant.
The account benefits will be taxable to the new beneficiary, to the extent that distributions are made. If the beneficiary is entitled under the employer's plan to rollover the account into an IRA, then that may defer tax liability.
Hope this helps.
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He would have to start taking MRDs immediately. There is no tax liability, if the account is treated as a "trustee-to-trustee" transfer, which means that it's not actually a new IRA, but rather the beneficiary of the account is treated as if he/she were the deceased participant.