Important Information Regarding Your FCC Issued Federal Registration Number

Applicants seeking an upgrade their existing amateur license should locate their FRN number, if they have been issued one, and bring it to any VE session for upgrade when they come in for an upgrade!  

If an FRN has been issued to you, it will be printed on the face of newer licenses.  Older licenses may not show the FRN, but you can locate it easily online.  The FRN is shown on your public information in the FCC's callsign lookup,  QRZ's callsign database (when you select "detailed information", and the ARRL callsign search . 

If you do not have an FRN, you will have to enter your SSN on your NCVEC 605, and the FCC will issue you an FRN when it issues your license. Upgrading hams without an FRN, or prospective hams who do not wish to release their Social Security Number (SSN) to a VE team can go online to register and obtain an FRN, although the process is a little cumbersome.

Why all the fuss?  Well, in what appears to be a change of policy by the FCC, the ARRL has informed amateur license applicants that the FCC will reject an application for license upgrade when the applicant provides a Social Security number (SSN) rather than the FRN number on the license application.  According to the March 9, 2007 "ARRL Letter":

Advisory to Amateur Radio license/upgrade applicants: Use your FRN! 

ARRL Volunteer Examiner Coordinator (ARRL VEC) urges all Amateur Radio license and upgrade applicants to use their FCC Registration Number (FRN) <https://svartifoss2.fcc.gov/coresWeb/publicHome.do>, if they have one, when completing Form 605, not their Social Security number. The FCC asks applicants to register via the FCC's COmmission REgistration System (CORES), to obtain an FRN, and it requires applicants to use their FRNs when filing
Form 605. The FRN uniquely identifies an applicant in all transactions with the FCC and avoids the need to provide a Social Security number on the application form. ARRL VEC Manager Maria Somma, AB1FM, says that if her
department submits license data to the FCC using a Social Security number when the applicant already has an FRN, the FCC rejects the data because an FRN already exists. Somma also reminds applicants and Volunteer Examiner
teams to attach any Certificate of Successful Completion of Examination (CSCE) for element credit to upgrade applications. Using your FRN and attaching any needed CSCE to your Amateur Radio application in Form 605 will
eliminate delays in obtaining your license or upgrade.

It is not clear whether this is a change in policy by the FCC, or whether the ARRL VEC has previously been looking up and supplying the applicant's previously issued FRN from FCC records to the FCC submitting the licensing information when the applicant provided only the SSN.  Regardless, if you have an FRN, you should bring it with you to the exam session!