Know you can just say 'no'
To protect your Social Security number, you can always refuse to give it when businesses ask for it. But they can deny you service, says Schifferle.
Still, don't just automatically fill in that blank on forms, says Grant. Be skeptical about why the business needs your number. She suggests offering your driver's license number instead.
At credit bureau TransUnion, spokesman Clifton O'Neal says credit reports can be pulled without Social Security numbers. But the additional information can allow a business to receive a more complete report about you.
TransUnion screens tenants and doesn't always need Social Security numbers to provide landlords with credit reports, O'Neal says.
Insurance companies might charge you higher premiums if you don't supply your number, warns J. Robert Hunter, insurance director for the Consumer Federation of America.
But spokeswoman Michal Brower says major insurer State Farm doesn't even ask.
Some state laws bar colleges and universities from demanding students' Social Security numbers, except for financial aid, says LeRoy Rooker, a senior fellow with the American Association of Collegiate Registrars and Admissions Officers, or AACRAO.
Most schools store students' numbers in a database but don't use them on transcripts, an AACRAO survey found.