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The trust filed a 1041 and sent an information letter to the grantor, showing the income."
If the trust filed a 1041, then the information from the 1099-R (including the name of the trust and the trust's EIN) was shown on that form and the trust now becomes the payer and the grantor is the payee.
See https://www.irs.gov/instructions/i1041#idm139674712727152
Consequently, the name of the trust and its EIN should be shown by the grantor.
