A trustee-to-trustee transfer of an IRA is never reportable on a Form 1099-R. If the originating IRA custodian reports such a transfer on Form 1099-R, it has done so in error and the Form 1099-R would need to be corrected to show that no distribution actually occurred.
A code-G Form 1099-R with the IRA/SEP/SIMPLE box marked for an actual distribution from a traditional IRA is only used to report a direct rollover to an employer plan like a 401(k). Code G is never to be used for moving one IRA to another IRA.
