An EFIN, or electronic filing identification number, is a unique number assigned to approved IRS e-filer providers, which allows these authorized companies to file taxes electronically, explains the Internal Revenue Service. The IRS requires firms to have an EFIN to file taxes electronically.
As of 2015, businesses looking to obtain an EFIN must complete an application and provide either an employer identification number or a Social Security number, notes the IRS. The IRS requires the doing-business-as name on the application, and the firm also has to list the company's address on the form, since a personal address is not allowed. The IRS reviews the application to check the suitability of the company after the company completes the application. If the business passes the suitability check, the IRS then sends the firm an acceptance letter that includes the EFIN. Providers can also use the EFIN for e-file activities such as return transmissions or return origination.