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 care, 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.

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. 

Who can bill CPT add-on codes?

Anyone who is qualified to bill CPT codes is also eligible to use add-on codes. 

Let’s say you’re a licensed mental health provider, and during a session, you provide psychotherapy along with medical evaluation and management services. Rather than billing for each service separately, you would bill the primary CPT code for the medical evaluation and management service, and then apply add-on code +90833 for the additional 30-minute psychotherapy session. 

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:

1. The code is listed as a Type I, Type II, or Type III add-on code.
2. 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.”
3. 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 almost never eligible for payment if it is the only procedure reported by a practitioner. However, there is one exception to this rule: the critical care add-on code +99292. 

For this exception to apply, a provider would need to have reported the base code (99291). On the same day, a fellow provider at the same practice, having treated the same patient, can then report add-on code +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.

H2: 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 Add-On Codes: These codes are directly linked to a specific set of primary procedure codes. They must be billed alongside their designated primary service and cannot be used independently. 
• Type II Add-On Codes: These codes are not tied to a predefined list of primary procedure codes. Instead, CMS allows insurers to determine which primary codes they consider appropriate for these add-ons. As a result, coverage and billing rules may vary by payer. 
• Type III Add-On Codes: These codes may be associated with some, but not all, of the primary procedure codes identified in the CPT Manual. CMS advises insurers that the list of primary procedure codes in the CPT Manual is not exhaustive, and they have the flexibility to establish their own coverage criteria. 

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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. 

CPT add-on codes, by definition, indicate which procedures are secondary. These codes can’t be billed without a primary code, and, notably, 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 billing guidelines to help you ensure you’re billing correctly. 

Accurate coding is crucial for proper reimbursement, but it can be time-consuming and complex. 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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What is the difference between medical billing and medical coding? 

Many confuse medical billing vs. coding, but they are different steps of the billing process. At larger organizations these might be separate roles, but for private practices it will likely be the clinician playing both parts. 

• Medical coding is the first step in the billing process, converting healthcare services into standardized CPT codes and ICD-10 codes for documentation.
• Medical billing is the second step in the billing process, using these codes to submit claims and ensure providers get paid.

For example, a dietitian provides a 60-minute medical nutrition therapy session. The clinician (or coder) assigns CPT code 97802 (initial assessment) for documentation. The clinician (or biller) submits the claim to insurance, and follows up for reimbursement. 

To learn more about insurance billing for private practice, access our step-by-step guide.

Coding and billing with Healthie

Healthie simplifies the coding and billing process by integrating billing software with automated claims management. Instead of manually tracking CPT codes, providers can rely on HIPAA-compliant billing software to organize primary and add-on codes, verify claims, and minimize denials.

By using Healthie, practices can:

• Automate billing process steps for efficiency and fewer errors.
• Ensure proper use of CPT codes and modifiers.
• Reduce your administrative workload by leveraging a top medical billing software.