The MAC (Medicare Administrative Contractor) is the Medicare contractor responsible for processing and paying Medicare claims for a certain geographic region. They are responsible for identifying and correcting Medicare overpayments and underpayments. In addition, the MAC is responsible for processing Medicare provider appeals.
One tool the MAC uses to target improper claims is prepayment edits. There are two types of prepayment edits: NCCI Edits (National Correct Coding Initiative) and MUE Edits (Medical Unlikely Edits). These are automated edits based on methodology developed using CPT coding guidelines and input from the AMA and other medical providers across the country. Medical providers may see these edits on their Medicare explanation of benefits.
NCCI & MUE Edits
The NCCI Edits are intended to promote correct coding methods and to control improper payments. Just because a claim hits an edit does not mean the claim is not payable. If the services were appropriate based on the specific circumstances and an appropriate modifier was used when the claim was billed, the claim can be eligible for payment. The provider’s medical record must contain information that supports the need for the service and the use of the modifier.

The MUE Edits attempt to reduce inappropriate payments by setting the “maximum units of service that a provider would report, under most circumstances, for a single beneficiary on a single date of service.” Because these edits are based on normal or average circumstances, sometimes the care provided for a patient may vary from the norm.
Given this possibility, there are several modifiers the medical provider can use to represent why or how service was provided. As with the prior edits, the provider’s medical record must contain information that supports the treatment given and the modifier used when billing. Documentation is vital to ensuring correct payment for medical services that were rendered.
In addition, to claim edits, the MAC utilizes a process known as the Medical Review Program. MACs perform data analysis to identify patterns in provider billing. If the MAC data analysis indicates that a provider-specific potential error exists, the MAC will review a sample of representative claims. This is called a “probe” sample. Usually, the sample is 20-40 claims.
If a medical provider receives a request for documentation under the Medical Review Program, this should raise a flag with the practice managers. Although it does not confirm that a problem or violation exists, it does confirm that Medicare has a suspicion that a problem exists and that they are looking into the issue further.
Great care should be taken in responding to this documentation request. The MAC is required to note on the request the reasons the claims have been targeted. The MAC must list the law, the NCD or the LCD that is the basis for the audit. In addition, the MAC should state what documentation is needed for the MAC to make their determination.