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NEC and NOS

Vijayarani Sivakumar

Published On - June 15, 2020

NOS is the more commonly used and means the provider did not give you the specifics. For example, “pain in limb.” You would use a NOS code because there are more specific codes available, but your provider did not state them.

Simply put, NEC means the provider gave you a very detailed diagnosis, but the codes do not get that specific.

Within ICD-10-CM, you may select codes defined as “Not Otherwise Specified” (NOS) when there isn’t enough documentation to select a more specific code. In other words, a deficiency in documentation prevents you from coding to a higher level of specificity.

NOS codes are never favored, and claims submitted with such diagnoses may be rejected for lack of medical necessity and/or specificity. When possible, you may wish to ask the documenting provider for additional information and/or to append the record, so that a more precise diagnosis may be selected.

Codes defined as “Not Elsewhere Classifiable” (NEC) may be selected when specific information is documented for the diagnosis, but there isn’t an existing ICD-10-CM code to report it. In this case, the ICD-10-CM manual—not the documentation—lacks additional specificity.

TIP: Codes titled “other specified” in the Tabular List usually (not always) have a number ‘8’ in the fourth or sixth character and/or a number ‘9’ in the fifth character.  This lets the coder know that the code is more likely an NEC or “not elsewhere classified” code. Codes in the Tabular List with “unspecified” in the title usually have a number ‘9’ in the fourth or sixth character and/or a ‘0’ in the fifth character.

Examples of NEC and NOS

C06.9 – This code is an example of NOS code. This means malignant (cancer) neoplasm of the oral cavity. Cancer may be in any part of the mouth. The exact part is not specified by the doctor.

Z48.89  - Aftercare following surgery, specified NEC

H25.89  - Cataract senile specified NEC