There is not a central Medicare office or department that handles the medicare providers and billing. There are several intermediaries that process all provider information, billing and payments. These intermediaries change from time to time. Now the intermediary for California Part A and Part b Medicare is Palmetto GPA. Palmetto GPA is the company you need to use to change or enroll as a medicare provider.
Making changes to a physicians medicare provider information can be difficult. Whether it is a change of address, adding an office address or changing other information, there are certain forms that must be filled out and sent to your medicare intermediary. The CMS 855 forms are generally used to apply to be a medicare provider or to make changes. For a new application see this Medicare web site. Any address change, phone or fax number change, name, specialty, contact person or billing agency must be reported to medicare within 30 days of the change. For changes only the section of the CMS 855B you are changing plus section 15 need to be completed and returned. See the chart on page 4 of CMS-855B booklet to see which sections you need to fill out. Remember that section 15 must be an original signature and all forms must be sent to medicare not faxed. Be prepared to take a few months for this process and additional forms may be required. The Medicare Provider Enrollment, Chain, and Ownership System (PECOS) can also be used to apply or change a providers information, but the registration process can be hard to maneuver.
If you are not already receiving your payments from medicare as direct deposits (electronic funds transfer), you will have to change to direct deposit when any other change is made. The EFT agreement form is used. Eventually this will probably be required for all Medicare providers.