Modifier 79
Unrelated procedure or service by the same physician during the postoperative period
Use it when
- A procedure during a global period addressing a completely different problem
- Surgery on a different anatomic site during another procedure's global window
- The same procedure performed on the contralateral side
Do not use it when
- A complication of the original surgery, which takes modifier 78
- A staged or planned procedure related to the original
- An evaluation and management service, which takes modifier 24
A worked example
A patient is six weeks into the 90-day global period following surgery on the right eye. Surgery on the left eye is now performed.
The second procedure is on a different anatomic site and is unrelated to the first, so modifier 79 applies. It is paid at the full rate and begins its own global period.
Practices sometimes hesitate to operate on the fellow structure during a global period, believing payment will be reduced. It will not — the global period attaches to the site operated on, not to the patient.
What decides it
The payment difference between modifiers 78 and 79 is substantial, which is why the distinction matters commercially as well as accurately. A related return pays the intraoperative component; an unrelated procedure pays in full.
Because modifier 79 starts a new global period, a patient can be inside two overlapping global windows for different sites. Tracking them separately is what prevents later services being wrongly bundled or wrongly billed.
The diagnosis on the claim should reflect the unrelated condition. An unrelated procedure reported under the original surgical diagnosis contradicts itself and invites review.
Denial codes this affects
Modifiers often confused with this one
Terms used here — Modifier · Denial · CPT Code
How we handle it — Medical Coding · Denial Management · Claims Management
Every CPT and HCPCS modifier with a guide
Coverage attestation
Evaluation and management
Global period
- 24Unrelated E/M in a Global Period
- 57Decision for Surgery
- 78Unplanned Return to the Operating Room
- 79Unrelated Procedure in a Global Period
- 58Staged or Related Procedure
Multiple and bilateral
Primary sources
What the payers and code-set maintainers actually publish about modifier 79.
- Global Surgery booklet (opens in a new tab)
Centers for Medicare & Medicaid Services — What the 10 and 90-day global periods include, and which modifiers break out of them. The authority behind most postoperative bundling disputes.
- Medicare Claims Processing Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — The operative manual for how Medicare claims must be coded, submitted, adjusted and appealed. When a payer policy and a vendor's advice disagree, this settles it.
- CPT code set (opens in a new tab)
American Medical Association — Maintainer of CPT. Annual changes to CPT are the most common cause of a sudden, unexplained rise in denials each January.
Questions about modifier 79
For a procedure during a surgical global period that is unrelated to the original surgery — a different problem, a different anatomic site, or the same procedure on the contralateral side. It is paid at the full rate.
Modifier 78 is a related, unplanned return to theatre for a complication, paid at the intraoperative rate only and not restarting the global period. Modifier 79 is an unrelated procedure, paid in full and starting its own global period.
Yes, with modifier 79. The global period attaches to the site operated on rather than to the patient, and payment is not reduced. Practices frequently hesitate here unnecessarily.
Yes, which means a patient can be inside two overlapping global windows for different sites. Tracking them separately prevents later services being wrongly bundled or wrongly billed.
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