An Electronic Funds Transfer (EFT) indicator (formerly DUNS+4), is a four-character suffix to the unique entity identifier. The suffix is created in SAM.gov on the Financial Information page of the entity registration to identify alternative Electronic Funds Transfer (EFT) accounts.
For more information about EFT indicators, please review this Answer page from the SAM helpdesk, FSD.gov:
What is an Electronic Funds Transfer (EFT) Indicator and how do I create one?