What Are CPT Add-On Codes?

Learn what CPT add-on codes are at Healthie. Discover which CPT codes and modifiers you should know, and how to write them.

One of the trickiest parts of running a medical practice is getting used to the technical aspects of insurance billing. This means becoming familiar with the CPT (Current Procedural Terminology) codes relevant to your branch of healthcare, and using appropriate modifiers and add-on codes to correctly bill for the services you’re providing. CPT add-on codes are a particular type of code which show insurers that you performed a secondary service in addition to a primary service.

What are CPT add-on codes?

Healthcare providers often perform several procedures on a patient in one session. CPT Add-on codes are a special list of codes that let insurers know which procedures were performed in addition to the primary procedure. 

Let’s say you’re a physician, and you perform a cesarean delivery, followed by a hysterectomy, in one surgery. Rather than billing for each procedure separately, you can simply use the correct CPT code for the delivery, and then apply the add-on code +59525 for the hysterectomy. 

CPT codes are managed by the American Medical Association (AMA), and are updated regularly. In the CPT manual, you’ll be able to recognize which codes are add-on codes in one of three ways:

  • The code is listed as a Type I, Type II, or Type III add-on code.
  • In the CPT Manual, the symbol “+” is used to indicate an add-on code. The descriptor will also often include phrases such as “each additional” or “list separately in addition to each primary procedure”.
  • The code will usually have a global surgery period of “ZZZ” on the Medicare Physician Fee Schedule Database.

Can a CPT add-on code ever be reported alone?

A CPT add-on code is “never eligible for payment if it is the only procedure reported by a practitioner”. But there is actually one exception to this rule: the critical care add-on code +99292. 

If another physician in the same practice as you reported the base code (99291) on the same day as you also treated the patient, you can report +99292. Remember - this is the only time a CPT add-on code can stand alone. In every other case, it won’t be valid unless it’s used in conjunction with a primary code.

Types of CPT add-on codes

The Centers for Medicare and Medicaid Services (CMS) have divided the add-on codes into three groups. This grouping depends on how contractors are required to process the codes. The types are:

  • Type I. These codes are associated with a limited number of identifiable primary procedure codes.
  • Type II. These aren’t associated with a specific list of primary procedure codes. CMS encourages insurers to develop their own lists of primary procedure codes for type II CPT add-on codes.
  • Type III. Some of these codes may be associated with some, but not all, of the specific primary procedure codes identified in the CPT manual. CMS reminds insurers that the primary procedure codes in the CPT manual are not exhaustive, and again encourage them to create their own list of primary procedure codes.

Combining CPT add-on codes and modifiers

If your practice uses CPT add-on codes for insurance billing, you’re probably in the habit of using modifiers to clarify information about the services you’re charging for. 

For instance, healthcare providers often use modifier 59 to indicate that grouping these procedures together was necessary under the circumstances. Another common modifier is modifier 51. This is frequently used to let insurers know which procedures were additional to the primary procedure. 

But CPT add-on codes, by definition, indicate which procedures are secondary. These codes can’t be billed without a primary code, and the fee is already discounted as it is a secondary procedure.

This is why add-on codes are “modifier 51 exempt” and, most of the time, you won’t need to use any modifiers with CPT add-on codes. However, you can always check the CPT manual for any exceptions if you're unsure.

How to write CPT add-on codes

Using CPT add-on codes is much like using primary CPT codes. The golden rule is simply to make sure you’re always using an add-on code in combination with a primary code (unless it’s code +99292). You can find a full list of CPT add-on codes in Appendix D of the CPT manual, which also includes guidelines to help you ensure you’re billing correctly. 

Making sure that you’re coding for your services correctly can be time-consuming. Practice management and billing software, such as Healthie, can make a big difference. Automating and streamlining the insurance claims submission process can remove a lot of the pressures that come with this important aspect of running a medical practice.

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