Medical Billing Tips: How (and How Not) to Use Common Modifiers


Did you know you might be expected to return money that insurance or third-party payers paid you? It’s not uncommon for optometry and ophthalmology practices to frequently misuse billing modifiers. When insurance and third-party payers determine you incorrectly used a medical billing modifier on a claim, this can become a costly mistake.

Modifiers are added to the Healthcare Common Procedure Coding System (HCPCS) or Current Procedural Terminology (CPT®) codes to identify why a doctor or other qualified healthcare professional provided a specific service and procedure.

To make it more complicated, payer rules for how to use modifiers vary with specific HCPCS and CPT billing codes. Not all modifiers can be used with HCPCS or CPT codes. It’s also critical that you keep up with Local Coverage Determinations (LCD) to ensure you are coding claims correctly.

Unfortunately, misusing medical billing modifiers can trigger an audit that can lead to hefty fines—audits can go back many years. Medicare audit fines might be as high as $10,000 for each occurrence. Which means every time you bill a modifier on a claim incorrectly, you may have to pay $10,000 for each occurrence. That adds up quickly.

Here are some red flags to look out for when billing with a few common modifiers. Knowing when and when not to use a modifier maximizes reimbursements and prevents denials and potential audits.

What are HCPCS and CPT Codes?

HCPCS codes are standardized five-character, alpha-numeric code sets used for billing Medicare and Medicaid patients that correspond to services, procedures, and equipment not covered by CPT codes. The Centers for Medicare and Medicaid Services (CMS) monitors HCPCS billing codes.

CPT codes are published by the American Medical Association® and consist of three types or categories of five-character codes and two-character modifiers to describe any changes to the procedure.

Medical Billing Modifier 24

Modifier 24 Definition: “Unrelated evaluation and management (E/M) service by the same physician or other qualified health care professional during a postoperative period.”

Modifier 24 is used when a doctor provides co-management services. It is only used to append to E/M codes. It’s important to keep accurate records that document the specific E/M service the patient received for the treatment of the underlying condition that was not related to the surgical procedure during the postoperative period.

For example, if a patient has cataract surgery and experiences complications in the eye not operated on—or if the patient suffers complications in the operated eye and it’s located in the region of the eye that was not impacted by the surgery—you can append modifier 24.


Never use modifier 24 if:

  • The surgical complication is considered part of the global surgery package.

  • The patient requires pain management related to the surgical procedure.

  • The patient is admitted to a skilled nursing facility for a condition related to the surgery.

  • Follow-up E/M visits are related to the patient’s recovery following surgery.

  • The postoperative period (10- or 90-day global period) is no longer valid. A global period consists of the time before, during, and after a surgical period that covers the patient care for the particular procedure.

  • Services were rendered on the same day as the procedure (refer to modifier 25).

What is the Global Period? A global period consists of the time before, during, and after a surgical period that covers the patient care for the particular procedure.

Medical Billing Modifier 25

Modifier 25 Definition: “Significant, separately identifiable evaluation and management (E/M) service by the same physician on the same day of the procedure or other service.”

Modifier 25 is used when you perform a procedure—and a significantly unrelated and separately identifiable E/M service—during the same session or the same day.

To support the elements of an E/M service that is above and beyond what a provider would perform for the procedure that same day, you must submit clear documentation showing why the procedure was necessary, and link modifier 25 to the appropriate E/M CPT code. While you do not need to use two different diagnosis codes, you must document both the E/M service and procedure.

For example, for some patients, you may need to report modifier 25 when “removing a foreign body or closing a punctum with a punctal plug.” However, many E/M services are often provided as a standard part of performing surgical services.

NEVER use Modifier 25 to:

  • Append to surgical codes, medical procedures, or diagnostic tests and procedures as payers will deny it as an invalid modifier combination.

  • Append to an E/M code that is explicitly used for a new patient and is not a procedure or other service code.

  • Bill for a doctor other than the doctor or other qualified healthcare provider performing the procedure.

  • Bill with a procedure or service with no global fee period (0, 10-day, or 90-day global period).

Medical Billing Modifier 55

Modifier 55 Definition: “Post-operative management care only.”

Modifier 55 is used to identify when a doctor performs the postoperative management and another doctor performs the surgical care only procedure (modifier 54).

According to the CMS Medical Learning Network Global Surgery Booklet, “The physician, other than the surgeon, who furnishes post-operative management services, bills with modifier 55. Use modifier 55 with the CPT procedure code for global periods of 10-days or 90-days. This modifier is not appropriate for assistant-at-surgery services or for ASC facility fees.”

CMS requires that doctors keep copies of the written transfer agreement in the patient’s medical record. You must also provide “at least one service before billing for any part of the post-operative care.”

During a recent aging claims report analysis with a Fast Pay Health client, we noticed a pattern of denials for postoperative claims that were consistently getting denied for missing information. By processing the claims with the Assumed Care date, Relinquished Care date, Surgeon (as referring provider) and modifier 55, the practice is now receiving full payments.

Never submit Modifier 55 with:

  • CPT codes that have a 0 days global period

  • E/M services

  • Global surgical split modifiers 54 and 56

  • Modifier 80 (assistant surgeon)

  • CPT 99024 (postoperative follow-up visit)

Medical Billing Modifier 59

Modifier 59 Definition: “Distinct Procedural Service.”

Modifier 59 is one of the most used modifiers. You should only use modifier 59 if you do not have a more appropriate modifier to describe the relationship between two procedure codes. Modifier 59 identifies procedures/services that are not normally reported together.

Modifier 59 is used if the same doctor or qualified healthcare professional performed an unrelated procedure on the same patient on the same day the doctor performed the office visit. For example, some optometry offices use modifier 59 to get paid for both OCT/GDX and fundus photography in the same visit.


Your documentation “must support a different session, different procedure or surgery, different site or organ system, separate incision/excision, separate lesion, or separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual.”

Though the National Correct Coding Initiative (NCCI) edits allow the use of modifier 59, determining if it is appropriate to use can be tricky.

Never attach modifier 59 to an E/M service. Depending on the local policy, if the tests are necessary due to two separately identifiable conditions, you may be able to link the appropriate diagnosis code to each CPT code and add modifier 59 to the second procedure. To report a separate and distinct E/M service with a non-E/M service performed on the same date, check to see if modifier 25 is appropriate.

CMS uses four sub-modifiers that replace modifier 59:

  • Modifier XE – “Separate Encounter: A service that is distinct because it occurred during a separate encounter.” Only use this to describe separate encounters on the same date of service.

  • Modifier XS – “Separate Structure: A service that is distinct because it was performed on a separate organ/structure.”

  • Modifier XP – “Separate Practitioner: A service that is distinct because it was performed by a different practitioner.”

  • Modifier XU – “Unusual Non-Overlapping Service: The use of a service that is distinct because it does not overlap usual components of the main service.”

Medical Billing Modifier 79

Modifier 79 Definition: “Unrelated procedure or service during a post-operative period.”

Modifier 79 is used for unrelated procedures provided by the same physician or other qualified health care professional during the postoperative period.

For example, if the patient has a complex cataract surgery (66982) on the right eye on March 1 and the doctor performs the same surgery on the patient’s left eye on April 1, the surgery on the left eye should be reported as 66982-79-LT.

It’s not uncommon to get postoperative claims paid incorrectly or not at all, especially when the surgery of a second eye takes place during the global period for the surgery that was performed on the first eye. When you use modifier 79 correctly, this allows the claim for the second eye to be paid. Remember, each eye’s global period (postoperative) runs independently of the other.

Never apply modifier 79 to office visits (see modifier 24) and only append to other unrelated surgery or procedures with a 90-day global period.

How to Use Informational Eyelid Modifiers

Common ophthalmic procedures for Level II HCPCS Medicare claims that require eyelid modifiers include Epilation (67820-67805), Punctal plug procedures (68760-68761), and Chalazion excision (67800-67805).

RT (right eye) and LT (left eye), and eyelid modifiers E1-E4 are used for the CPT® codes listed above to provide additional information about the services provided, such as anatomical site.

  • E1 Modifier: A service was performed on the upper left eyelid

  • E2 Modifier: A service was performed on the lower left eyelid

  • E3 Modifier: A service was performed on the upper right eyelid

  • E4 Modifier: A service was performed on the lower right eyelid


Medical Billing Best Practices

The financial health any eye care practice depends on complete ophthalmology and optometry billing solutions and revenue cycle management. It’s critical to pay close attention to using modifiers correctly, accurately documenting patient records and physician notes, and ensuring claims are not under or over-coded.

While all optometric practices will experience claim rejections and denials, at Fast Pay Health, we know the ins and outs of insurance and third-party payers best. Knowing how to prevent rejections and denials in the first place is the best “cleaning solution” to receiving revenue quicker.

Fast Pay Health optometric billng consultants are experts at making sure medical claims are clean and free from errors before we submit them. Coders are well versed in CPT and ICD-10 coding and billing with code modifiers.

Request a free practice analysis today and start reaping the benefits of fewer denied claims and faster payments.

Related: Common Coding Denials You Need to Know for Fast Payments

Related: 6 Eye Care Billing Rejections You Can Overcome