Ledgers, operating units and flexfields — with Subledger Accounting already in the picture.
EBS R12 encodes accounting through the Accounting Flexfield, ledgers and operating units under Multi-Org Access Control, and Subledger Accounting with the Accounting Methods Builder. D365 F&O replaces the flexfield with a main account plus financial dimensions governed by account structures, and redistributes SLA rule logic across posting profiles and dimension defaulting. Operating units are the trap: they carry policy variance inside a single ledger and must not be reflex-mapped to legal entities. TCA parties, supplier sites and customer site uses are richer than D365 party placement, and the concurrent-program and open-interface estate is operationally central but not portable.
Accounting Flexfield + SLA / AMB → Main account + financial dimensions + posting profiles