Modifier 58 (Staged or related procedure/service by the same physician during the postoperative period) indicates that a subsequent procedure performed by the same provider during the global/postoperative period was planned, more extensive than the original, or therapeutic following a diagnostic procedure. The CPT/AMA and CMS definitions specify that if the subsequent procedure meets at least one of those criteria and occurs within the original global period, modifier 58 should be appended and the global period for the subsequent procedure is restarted. CMS’s Global Surgery MLN booklet emphasizes that modifier 58 restarts the global surgical period and distinguishes it from unplanned returns to the OR (modifier 78). All three criteria in the definition are connected by “or,” so meeting any one is sufficient to qualify for modifier 58.

Using modifier 58 signals to payers that the second procedure is separate and may be payable rather than bundled into the initial global surgical package. Practically, appending modifier 58 resets the global period so the subsequent procedure can be billed and reimbursed as a distinct episode of care. AAPC guidance notes modifier 58 is frequently underused and that correct application preserves appropriate reimbursement for legitimately staged or therapeutic follow-up procedures.

Modifier 58 must be distinguished from similar modifiers: modifier 78 denotes unplanned returns to the operating room for complications during the postoperative period (and does not restart the global period), while modifier 79 denotes unrelated procedures by the same provider during the postoperative period. Modifier 58 is also not the correct choice for same‑day related or unrelated procedures—those situations may require modifier 59 or an appropriate X{EPSU} modifier. The CMS and AAPC sources and coding guidance provide real-world examples (e.g., planned axillary dissection after lumpectomy, delayed repair after excision with pathology confirmation, staged flap division) to illustrate appropriate use within the original global period.