Notes on payer behavior

CO-97: bundling, global periods, and the remark code that decides

Clearia · August 2026 · denial codes, read properly

Denial code CO-97 is the payer saying: "The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated." What that means for your practice, and whether it's worth chasing, below.

CO-97, "the benefit for this service is included in the payment for another service," is the bundling code. It's really two different denials wearing one number. Which one you've got is written in the remark code next to it, and the two branches have completely different plays.

The remark code decides the branch

The standard requires CO-97 to travel with a remark code (RARC). The remark is your routing instruction:

• M144 or N525: the payer says the service falls inside a surgical global period.
• M15, M80, or N19: a code-pair bundling edit (NCCI).
• No corresponding edit on file: a payer-proprietary bundling rule. The play is an appeal citing the payer's own published policy, because there's no national edit behind it.

This read-the-remark habit applies well beyond 97. The CO-16 note covers it.

Branch one: the global period, where date math wins

Surgical procedures carry a global window, commonly 10 or 90 days, inside which related visits and procedures are considered paid with the surgery. Two things go wrong, and both are checkable:

• The window is miscounted. A 90-day global is really a 92-day window (the day before, the day of, and 90 days after). A 10-day global is an 11-day window with no pre-op day. Payers apply the wrong window more often than you'd think. Pull each code's global indicator from the Medicare fee-schedule file and count.
• The service wasn't related. The modifier arsenal exists precisely to say so: 24 (unrelated visit during the global), 25 (significant, separately identifiable same-day visit), 57 (the decision for surgery), 58 (staged procedure), 78 (return to the operating room), 79 (unrelated procedure). Which modifier fits is a chart question. That they exist at all is why a global-period denial is a beginning, not an end.

The pattern spans every surgical specialty: cataract surgery in ophthalmology (90-day global, high volume), fracture care in orthopedics and hand surgery, excisions and repairs in dermatology (mostly 10-day globals), ENT and urology procedures alike. Two payer-error patterns worth knowing. First, modifier 25 does not require a different diagnosis from the procedure. The national edit manual says so, and payers still deny on same-diagnosis grounds anyway. Second, as of 2025, Medicare requires transfer-of-care modifiers (54/55) on all 90-day globals, so surgical care and post-op care split between practices is a new place where correctly billed claims get wrongly bundled.

Branch two: bundling edits. Check the indicator first

For code-pair edits, one fact controls everything: the edit's modifier indicator. Indicator 1 means a bypass modifier is allowed when the services were genuinely distinct. The play there is a corrected claim with the most specific modifier the documentation supports (the X-modifiers over generic 59). Indicator 0 means no modifier ever bypasses the edit. No appeal changes that. Your honest options are a coding correction or acceptance.

The add-on-code cousin

A near neighbor of the bundling denial is the add-on code denied because its required primary procedure wasn't found. That's a linkage problem, not a coverage problem, and the fix depends on where the primary went. Primary denied upstream? Fix the primary and the add-on follows. Primary paid on a separate claim? Appeal citing the paid claim's number and date so the payer links them. Primary genuinely omitted? A corrected claim billing both together, properly sequenced, cures it. Endoscopy add-ons in GI, additional-lesion codes in dermatology, and additional-level codes in spine injections all live in this pattern.

Which door: corrected claim or appeal

The mode matters as much as the argument. A modifier that should have been on the claim and wasn't goes back as a corrected claim: a replacement referencing the original claim number, not a letter. An appeal is for the case where the modifier was billed correctly and denied anyway, or where the edit is payer-proprietary. Then the letter cites the documentation and the payer's own policy. Send a letter to fix a coding omission, or resubmit to overturn a judgment call, and you've wasted a clock you don't get back.

When not to appeal

Indicator-0 pairs, and services that genuinely were components of the primary procedure. Appealing correctly bundled services wastes the appeal window and teaches the payer to read every future letter from your practice as noise. The distinct-service claim has to be true in the chart before it goes in a letter.

And the shortfall side of bundling, where your contract says a service is separately payable but it paid at zero, is underpayment territory. That comes with a 12-month statutory life in Florida on fully-insured business.