Modifier 79: Unrelated Procedure During a Global Period

Modifier 79 is a billing modifier that tells Medicare a procedure done inside another surgery's global period has nothing to do with that first surgery. Without it, Medicare treats a second procedure by the same surgeon during the postoperative window as part of the original package and denies it; with it, the new procedure is paid normally and starts its own global period.

When to use modifier 79

Medicare's global surgical package covers the surgeon's related care from the day before a major surgery (or the day of a minor one) through the end of the postoperative period. Anything the same surgeon bills in that window is assumed to be part of the package unless a modifier says otherwise. The Claims Processing Manual (Pub. 100-04, ch. 12, §40.4.A) says a procedure with its own global period, billed during a prior procedure's postoperative period without 58, 78 or 79, should be denied.

Use 79 when all of these are true:

• The new service is a procedure with a 000, 010 or 090 global indicator. Check the global days on the code page, or run the dates through the global period calculator.
• The same surgeon, or a partner in the same group and specialty, billed the earlier surgery. CMS's global surgery booklet (MLN907166) treats same-group, same-specialty providers as one surgeon.
• The new procedure is unrelated: a different problem, a different body part, or a new condition, not a complication or a planned next step.

Example. A surgeon replaces a patient's right knee (27447) on March 2, 2026. In May the patient tears the meniscus in the left knee and the same surgeon performs an arthroscopic meniscectomy (29881). Bill 29881-79-LT with the left-knee diagnosis.

When not to use modifier 79

• The procedure treats a complication of the first surgery and needs the operating room. That is modifier 78, and Medicare pays only the intraoperative portion.
• It was planned at the first surgery, is more extensive, or is therapy after a diagnostic procedure. That is modifier 58.
• It's an evaluation and management visit. Unrelated postoperative visits take modifier 24; a separate visit on a procedure day takes modifier 25.
• The code has an XXX global indicator. Medicare pays these without a global-surgery modifier (ch. 12, §40.4.A).

How modifier 79 affects payment

Modifier 79 carries no percentage. The unrelated procedure is paid at its full fee schedule amount, subject to the usual multiple-procedure rules if other procedures are done the same day (modifier 51). Two other effects matter:

• A new global period starts on the date of the unrelated procedure (ch. 12, §40.2.A.7). Visits related to it are now bundled into its own package.
• The first global period keeps running. Follow-up for the original surgery is still included until its own window closes.

Modifier 79 vs 58, 78 and 24

The difference between 79 and 59 is timing. 79 separates a procedure from a surgery's postoperative period; 59 separates two procedures on the same day from an NCCI edit. A same-day unrelated procedure in another surgery's global window can need both.

FAQ

When should I use modifier 78 vs 79?

Use 78 when the second procedure is related to the first surgery, usually a complication, and needs a return to the operating room. Use 79 when it has nothing to do with the first surgery. 78 pays only the intraoperative share and adds no new global period; 79 pays in full and starts a new one.

What is an example of modifier 79?

A surgeon removes a patient's gallbladder, and six weeks later, still inside that 90-day global period, the same surgeon repairs the patient's unrelated inguinal hernia. The hernia repair is billed with 79 and its own diagnosis.

What is the difference between modifier 79 and 59?

Modifier 59 tells Medicare that two procedures on the same day weren't overlapping, so an NCCI bundling edit shouldn't apply. Modifier 79 tells Medicare that a procedure falls inside an unrelated surgery's global period. They solve different denials and can appear on the same line.

Does RT/LT or 79 go first?

79 goes first. Noridian, for example, tells providers to append 79 in the first position as a pricing modifier, with anatomic modifiers such as RT or LT after it: 29881-79-LT.

Does modifier 79 start a new global period?

Yes. CMS says a new postoperative period begins when the unrelated procedure is billed (Pub. 100-04, ch. 12, §40.2.A.7).

Keep reading

• Modifier 58 and modifier 78, the other two procedure modifiers in the global period.
• Modifier 24 for unrelated visits, and modifier 57 for the visit that decides on surgery.
• Global period calculator to find the window for any surgery date.
• Modifier 25 vs 59 for same-day visit and procedure questions.
• Codes on this page: 27447 29881 47562 49505

Sources: CMS Medicare Claims Processing Manual, Pub. 100-04, ch. 12, §§40.1, 40.2.A.7 and 40.4; CMS MLN907166, Global Surgery (December 2025); Noridian JF Part B, Modifier 79 (updated May 9, 2025). Verified October 6, 2026.