Billing modifier · CMS claims manual

Modifier 51: additional procedures at the same session.

Modifier 51 goes on the additional surgical procedures a physician performs on the same patient on the same day. The most major procedure is reported without it. Under the standard Medicare rule, the highest valued procedure is paid at 100 percent and the second through fifth at 50 percent.

Sources: CMS manuals · retrieved November 2, 2026Reference page · nothing is sent or stored

Modifier 51 at a glance

Modifier: 51: Multiple Procedures
Used on: Additional surgical procedures by the same physician on the same day
Medicare rule: Most major procedure has no 51; indicator 2 codes paid 100% then 50% for the second to fifth
Primary source: CMS Ch. 12 s.40.6

What CMS says

CMS chapter 12, section 40.6 defines multiple surgeries as separate procedures performed by a single physician, or physicians in the same group practice, on the same patient at the same operative session or on the same day, for which separate payment may be allowed. They are different from procedures that are components of, or incidental to, a primary procedure; those are not separately billable.

Billing instruction: report the more major surgical procedure without modifier 51, and report additional procedures by the same surgeon on that day with modifier 51. Major is decided by the Medicare fee schedule approved amount, not by the amount you charge.

How Medicare pays it

For codes with multiple surgery indicator 2, the MAC ranks the procedures by fee schedule amount and pays the lower of the billed amount or 100 percent for the highest, and 50 percent for the second through fifth. A sixth or later procedure is suspended for review and paid “by report,” never below 50 percent of the full amount.

Worked example with hypothetical fee schedule amounts: procedure A $900.00, procedure B $500.00, both indicator 2. A is paid up to $900.00 and B up to $250.00 (50 percent), a total of up to $1,150.00. Listing B first on the claim does not change the ranking.

Indicator 3 (endoscopies) uses a different rule: the full value of the highest endoscopy plus the difference between the next endoscopy and the base endoscopy. CMS’s own example pays $374.56 + ($285.98 - $255.40) = $405.14.

Limits

If two physicians each perform distinctly different, unrelated surgeries on one patient on the same day (CMS mentions some multiple trauma cases), the multiple surgery rules may not be appropriate and modifier 51 is not used unless one surgeon individually performs multiple surgeries.

In an ambulatory surgical center, chapter 14 says services billed with modifier 52 or 73 are not subject to the multiple procedure discount.

Look-alike modifiers

Modifier 50: The same procedure on both sides.
Modifier 62: Co-surgeons on one procedure.
Modifier 59: Distinct procedural service.

The full modifier descriptions are in the AMA CPT code book and the HCPCS Level II code set; this page covers only what the CMS claims manuals say about modifier 51.

Sources

CMS: Medicare Claims Processing Manual, Chapter 12 (Rev. 13753, issued 05-07-26) — section 40.6, claims for multiple surgeries (retrieved 2026-11-02)
CMS: Medicare Claims Processing Manual, Chapter 14 (Rev. 13836, issued 06-24-26) — section 40.5, payment for multiple procedures (ASC) (retrieved 2026-11-02)

Every rule above was read from these CMS pages on November 2, 2026. Payers revise policies and contracts, so confirm anything that affects a claim with the payer or your Medicare Administrative Contractor.

Frequently asked questions

Which procedure gets modifier 51?

Every additional procedure. CMS says to report the more major procedure, ranked by fee schedule amount, without modifier 51.

What does Medicare pay for modifier 51 procedures?

Under the standard rule for indicator 2 codes: 100 percent for the highest valued procedure and 50 percent for the second through fifth.

Does modifier 51 apply to component procedures?

No. CMS distinguishes multiple surgeries from procedures that are components of or incidental to a primary procedure, which are not separately billable.

Not legal, billing or medical advice

This page explains published CMS manual text. It cannot see your claim, your contract or any payer’s policy. Confirm with the payer or your Medicare Administrative Contractor (MAC) before you bill, resubmit or appeal.