Providers and suppliers, that expect to receive payment from Medicare for services provided, are required to agree to receive Medicare payments through electronic funds transfer (EFT) at the time of Medicare enrollment, enrollment change request or revalidation.

Source:  http://www.palmettogba.com/palmetto/providers.nsf/ls/J1B~8QUKEL3366?opendocument&utm_source=J1BL&utm_campaign=J1BLs&utm_medium=email