Billing modifier · CMS claims manual

Modifier 50: a bilateral procedure on one claim line.

Modifier 50 reports a procedure performed on both sides of the body in the same operative session, on one claim line with one unit. Under the Medicare physician fee schedule, a code with bilateral indicator 1 is paid at the lower of the billed amount or 150 percent of the fee schedule amount.

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

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Modifier 50 at a glance

Modifier
50: Bilateral Procedure
Used on
Procedures done on both sides in one operative session
Medicare rule
One line, one unit; payment is the lower of billed or 150% of the fee schedule when the bilateral indicator is 1
Primary source
CMS Ch. 12 s.40.7; Ch. 4 s.20.6.2
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What CMS says

CMS chapter 12, section 40.7 defines bilateral surgeries as procedures performed on both sides of the body during the same operative session or on the same day. If a procedure is not identified by its own terminology as bilateral (or unilateral or bilateral), the physician reports it with modifier 50, as a single line item.

CMS notes that this differs from the CPT coding guidelines, which indicate that bilateral procedures should be billed as two line items. For Medicare, follow the one-line instruction.

When not to use it

Do not append modifier 50 when the code’s own terminology already says “bilateral” or “unilateral or bilateral.” CMS gives codes 27395 and 52290 as examples. The fee schedule already reflects the extra work, so the bilateral payment rules do not apply to them.

In the hospital outpatient setting, chapter 4 adds that modifier 50 is restricted to operative sessions, that one unit of service is reported, and that modifiers RT and LT are not reported when modifier 50 applies.

How Medicare pays it

The A/B MAC reads the bilateral indicator (Field 22 of the Medicare fee schedule database). Indicators 0, 2 and 3 mean the bilateral adjustment does not apply and payment is the lower of the billed amount or 100 percent of the fee schedule amount. Indicator 1 means the standard adjustment applies: the lower of the billed amount or 150 percent of the fee schedule amount.

Worked example with a hypothetical $400.00 fee schedule amount on an indicator 1 code: one line with modifier 50 and one unit is paid at up to $400.00 x 150% = $600.00, not $800.00 for two full units.

CMS also says the MAC identifies bilateral surgeries either by modifier 50 or by the same code on two lines reported once with LT and once with RT.

Look-alike modifiers

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 50.

Sources

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

Is modifier 50 reported on one line or two?

One line with one unit for Medicare. CMS says this differs from the CPT guidelines, which indicate two line items.

What is the Medicare payment for modifier 50?

For codes with bilateral indicator 1, the lower of the billed amount or 150 percent of the fee schedule amount. For indicators 0, 2 and 3 the adjustment does not apply.

Can I add modifier 50 to a code that already says bilateral?

No. CMS says not to report modifier 50 on procedures identified by their terminology as bilateral or as unilateral or bilateral.

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.

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