Global Surgical Period & Post-Op Modifier Decision Calculator
Compute the exact pre-op/post-op window for a surgery date, test whether a visit falls inside it, and pick the global-period modifier that matches what actually happened.
CMS Global Windows and the Modifier Decision That Follows
Window arithmetic per the CMS MLN Global Surgery booklet and Medicare Claims Processing Manual Pub. 100-04 Ch. 12 §40: a 090 window spans 92 calendar days (the day before surgery, the day of surgery, and 90 days after) — the most common counting error in post-op billing. Count calendar days from the procedure date, never the discharge date.
| Circumstance inside the window | Modifier (own wording) | Starts a new global? |
|---|---|---|
| E/M visit unrelated to the surgery | 24 — unrelated E/M during post-op | No |
| E/M visit where the decision for major surgery was made | 57 — decision for surgery | No |
| Significant, separately identifiable E/M with a minor procedure | 25 — separate E/M, same day as minor procedure | No |
| Staged or planned related procedure | 58 — staged/planned, more extensive, or therapy after diagnostic surgery | Yes |
| Unplanned return to the operating room for a related complication | 78 — related return to OR | No (intra-operative portion paid) |
| Procedure unrelated to the original surgery, same physician | 79 — unrelated procedure during post-op | Yes |
KX modifier threshold: have you crossed $2,480 this year?
For CY 2026 the KX threshold is $2,480 for PT and SLP combined and $2,480 separately for OT (CMS Therapy Services CY 2026 update; re-confirmed at each November re-check). Crossing it is not a cap and not permission: append KX only on claims where continued therapy is medically necessary and the record documents it. The year-to-date fields in the allocator above run this check on every calculation.
Frequently Asked Billing Questions
Is a 90-day global period 90 or 92 days long?
The package spans 92 calendar days: 1 day before surgery plus the day of surgery plus 90 post-operative days. The window end date is surgery date + 90 days.
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