In digital communication systems employing binary phase-shift keying and non-data-aided carrier phase recovery, a 180°carrier phase ambiguity is inevitable. Here, we propose a simple modification to the standard regular repeat-accumulate (RA) code structure by exploiting the differential encoding inherent to the inner encoder of RA codes resulting in codes that are 180°rotationally invariant. The proposed code structure exhibit performance virtually identical to that of standard regular RA codes with zero carrier phase offset under both zero and 180°carrier phase offsets with negligible additional hardware complexity.