ZIP codes requiring a nine-digit ZIP code (ZIP +4)

The payment locality for services paid under the Medicare physician fee schedule and anesthesia services is determined by using the ZIP code where the services were rendered. Some ZIP codes fall into more than one payment locality. The CMS ZIP code file uses the convention of the United States Postal Service which assigns these ZIP codes into dominant counties. In some cases, though the service may actually be rendered in one county, per the ZIP code it is assigned into a different county. This causes a payment issue when each of the counties has a different payment locality and therefore a different payment amount. 

Additions and deletions to the ZIP code file can be found at https://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/ProspMedicareFeeSvcPmtGen/index by clicking on the “ZIP Code Changes for [month, year]” file. To view all ZIP codes requiring a plus four ZIP code extension, click on the “ZIP Codes requiring +4 extension” file. Upon the release of a new quarterly update, the previous quarter’s additions and deletions are no longer displayed on the “ZIP Code Changes” file since they are included in the new “ZIP Codes requiring +4 extension” file.

Claims for services rendered in any locality requiring but not containing a nine-digit ZIP code, will be returned as unprocessable.

There are two instances in which you do not need to submit the nine-digit ZIP code on claims for services payable under the MPFS and for anesthesia services: 

• You may continue to submit claims with five-digit ZIP codes if you provide these services in areas that are not listed above and do not cross payment localities;
• There is no current requirement for the submission of a ZIP code when the place of service (POS) is “Home” (POS 12) or any other place of service that your Medicare contractor currently considers to be the same as “Home.” 

As necessary, CMS will provide quarterly updates to the list of ZIP codes that cross over into other localities.