What Are CPT Modifiers And Why Medical Billing Companies Use Them?

Since medical procedures and services are often complex, we sometimes need to supply additional information when we’re coding. CPT modifiers may describe whether multiple procedures were performed, why that procedure was necessary, where the procedure was performed on the body, how many surgeons worked on the patient, and lots of other information that may be critical to a claim’s status with the insurance payer.

Some of the common reasons for using a Modifier are:

  • The procedure was more complicated than anticipated
  • Another procedure was required during the same procedure
  • The same diagnostic test had to be re-run on the same day
  • The X-Ray was done in one facility and the results were read in a different facility

Consider this example: while doing surgery for a wrist repair – 25607, during the same procedure, a carpal tunnel release – 64721 is done.  You need to append modifier 51 to show the secondary procedure was performed.

CPT Modifiers are always two characters and may be numeric or alphanumeric. Most of the CPT modifiers you’ll see are numeric, but there are a few alphanumeric Anesthesia modifiers also. CPT modifiers are added to the end of a CPT code with a hyphen. In the case of more than one modifier, you code the “functional” modifier first, and the “informational” modifier second. The distinction between the two is simple: you always want to list the modifiers that most directly affect the reimbursement process first.

Take, for example, the partial mastectomy of the left breast (code 19302-LT-53). If you were to swap out the -53 (discontinued procedure) with the functional modifier -52 (for reduced services), you would then code the whole procedure 19302-52-LT. Note that the functional modifier (-52) now comes before the informational modifier (-LT). If the informational modifier is listed first in a claim, an insurance company will deny that claim and return it to the healthcare provider.

In CMS-1500 and UB-04 forms, the two most common claim forms, have space for four modifiers, payers don’t always look at modifiers after the first two. Because of this, you always want the most important modifiers to be visible.

Let’s take a quick look at an example of a CPT modifier in action.

A surgeon performs a procedure to remove a bone cyst in the upper arm of a patient. The procedure also includes obtaining a graft from elsewhere in the body. Due to minor complications, the surgeon is unable to fully excise the bone cyst. For the procedure, we’d code 23140 for “excision or curettage of bone cyst or benign tumor, humerus; with autograft (includes obtaining the graft).” Since the procedure was completed but not fully successful, we’d add the -52 modifier, for reduced services, to the code, and we’d end up with 23140-52.

Certain modifiers also have guidelines specific to them. The modifier -51, for multiple procedures, is one of the more commonly used CPT modifiers. In the instance of multiple procedures provided by the same specialist or healthcare provider, a coder would list the initial procedure’s CPT code, then append the modifier -51 to the end of the code for the additional procedure or procedures. Certain procedures, however, are listed in the CPT book as “-51 exempt,” and coders must be aware of this distinction.

Note that some modifiers can be used in conjunction with each other (like -23, unusual anesthesia, and -47, for anesthesia by the surgeon). Others contradict one another and cannot be included in the same code, For example, the modifier –LT (procedure on the left of two paired appendages or organs) cannot be coded with the modifier -50, which describes a bilateral procedure.

Payers have what is called reimbursement edits for reporting code combinations. If using two codes are stand-alone codes they may be subject to multiple procedure payment reductions. You would append modifier 51 to the procedure that has less value than the primary procedure. You need to be aware of special rules that are applied when using modifiers.

Using the appropriate modifiers can substantially impact reimbursement. If you do not report a modifier and the procedure allows a modifier you will not be paid for the procedure. There are industry standards related to the use of modifiers and reimbursement. While some modifiers change the payment rates some are for informational use only or impacts bundling edits. It pays to understand and get familiar with modifiers and how they are used.  Modifiers have different pricing, some pay 10% of the fee schedule and some pay 100%.

These are just a few examples to show the impact of modifiers:

Sr. No. Modifier type Details Reimbursements
1 Modifier 22 Increased Procedural services Maximum of 110% of Fee Schedule Allowance/Contracted Rate with supporting documentation
2 Modifier50 Bilateral Procedure 150% of Fee Schedule Allowance/Contracted Rate Submit one line with one unit
3 Modifier 51 Multiple Procedures 50% of Fee Schedule Allowances/Contracted Rate for each additional procedure unless the procedure is exempt from multiple procedure logic
4 Modifier 55 Follow up care only 20% of Fee Schedule Allowance/Contracted Rate
5 Modifier XE Separate encounter, distinct service Informational /impacts bundling


  1. Centre of Medicare and Medicaid Services (CMS), Global Surgery Booklet (Sept 2018). Retrieved from https://www.cms.gov/Outreach-and-Education/Medicare-Learning-Network-MLN/MLNProducts/downloads/GloballSurgery-ICN907166.pdf
  2. Ingenix Coding Lab-Understanding Modifiers. Retrieved from https://www.optum360coding.com/upload/pdf/3989/ICL-Understanding%20Modifiers.pdf