How Are ICD and CPT Codes Different—and Why Are They Important?

ICD codes and CPT codes are two of the most important coding systems to understand in the billing process. 

Whether you’re billing for health care services through insurance or using a superbill, the payer will need several key pieces of information in order to understand what you’re billing for and determine whether (and how much) to pay for it. 

Because larger payers receive millions of claims each year, this key information is usually provided in codes for efficiency. 

Below we’ll go into more detail about ICD and CPT codes, what they communicate, why they’re so important, and how to find the right code from an ICD and CPT codes list when you’re not sure. 

First, what are ICD and CPT codes?

If you’re wondering, “What are CPT codes?” or “What’s the difference between ICD 10 and CPT codes?” we’ll explain below. (Check out the most common mental health ICD-10 codes and common CPT codes from over 200,000 U.S.-based clinicians who use SimplePractice’s HIPAA-compliant electronic health record (EHR) system to manage their practices, minimize administrative work, and streamline filing and tracking insurance claims.)

Why we need ICD-10 diagnosis codes lists

ICD codes, aka International Classification of Disease codes, describe the client’s diagnosis. 

In other words, they refer to the specific condition that’s being treated, such as attention-deficit disorder (ADHD), predominantly inattentive type or generalized anxiety disorder (GAD). 

The World Health Organization (WHO) developed ICD codes for worldwide use. 

ICD codes are not only used in the process of health care billing, they’re also used to identify health and disease trends across countries. 

Simply put, they’re the standard diagnostic language used by health care providers, payers, researchers, and global public health officials. 

How frequently are ICD codes updated?

New ICD codes come out on an irregular basis, with minor updates published every one to four years. 

Entirely new versions of the ICD, which typically include more significant changes in coding and structure, launch far less often. 

The current version, ICD-10, entered common use in 1994. 

The ICD-11 launched in May 2019 and entered common use on January 1, 2022.

What are CPT codes?

CPT codes are Current Procedural Terminology codes.

In plain language, CPT codes describe clinical procedures and diagnostic and care activities in the healthcare system. 

In other words, they explain what the health care provider did during an interaction with or for a client or patient. 

The American Medical Association (AMA) developed CPT codes.

From federal government programs like Medicare and Medicaid, to private payers like insurance companies, CPT codes are the standard procedural language used across health care in the US. Here’s how to look up CPT codes.

How frequently are CPT codes updated?

New CPT codes come out several times each year to keep up with new developments in health care services.

Most health care providers primarily use the five-digit CPT codes considered Category I. In billing, you’ll typically use these codes most often. Category I CPT codes identify specific, well-established procedures. 

With some meaningful exceptions, U.S. insurers typically must pay for Category I procedures performed by a qualified health care professional when they are medically necessary to treat a client or patient’s condition. 

Category II CPT codes gather information about quality of care.

Finally, newer procedures and technologies use Category III CPT codes. 

What’s the difference between ICD-10 and CPT codes?

What makes ICD and CPT codes different from each other is the type of information they convey. 

CPT codes refer to the treatment, while ICD codes refer to the diagnosis or issue that the treatment aims to support or resolve. 

ICD and CPT codes are used hand-in-hand to quickly provide payors specific information about the specific service performed, which is defined by the CPT code, and why the service was performed, defined by the ICD code.

How to find an ICD-10 diagnosis codes list

You can find ICD-10 diagnosis codes online in a variety of formats. 

Search the official ICD-10 online, or browse the official ICD-11 online. A number of websites index ICD codes as well. This makes it easier to find the code you need in online searches. 

If you’re a mental health care provider and looking to determine an ICD code on the basis of a DSM diagnosis, you can use various online “crosswalks” to find the right ICD code. 

Naturally, it’s important to review the language of that code on the official ICD site. Diagnostic indicators and requirements of the DSM-5 don’t always line up perfectly with the diagnostic indicators and requirements in the ICD.

How to find a CPT code list

You can order the most current CPT code list as a manual in book form, but given how often codes are updated, you would need to regularly order newer versions. 

It’ll likely be easier to look up codes within your private practice insurance billing software, such as SimplePractice. 

Be sure to check the AMA website’s section specific to current CPT codes. This will help ensure your billing coding knowledge is accurate and up-to-date as the AMA issues new codes several times per year.

SimplePractice makes it easy to create, submit, track, and reconcile insurance claims all in one place—no more spreadsheets, separate logins, or ledgers.

Sign up for a free, 30-day trial to experience the time-saving benefits of using SimplePractice for your billing and insurance claims.

While the number of unique ICD and CPT codes mental health clinicians need to use can seem overwhelming, once you develop a basic understanding you’ll have the foundation you need to accept and bill insurance in your private practice. 

That means you’ll have the opportunity to offer care to more clients, grow your practice—and increase your impact.

How SimplePractice streamlines running your practice

SimplePractice is HIPAA-compliant practice management software with everything you need to run your practice built into the platform—from booking and scheduling to insurance and client billing.

If you’ve been considering switching to an EHR system, SimplePractice empowers you to run a fully paperless practice—so you get more time for the things that matter most to you.

Try SimplePractice free for 30 days. No credit card required.

READ NEXT: The 20 Most-Billed ICD-10 Codes in Mental Health