If you moved in the past year, you probably sent an e-mail to friends and family with your new mailing address. Did you also remember to write a letter to the IRS (technically, it's called Form 8822)? If not, there's a chance that the IRS tried to mail you a tax refund check, but it came back as undeliverable. That's assuming your tax return had your old address.
Back in 2011, the IRS was sitting on more than $150 million in tax refunds for nearly 100,000 people whose addresses were undeliverable. The average check was $1,547 [source: IRS]. If you think that the IRS owes you a refund, visit the aptly named Where's My Refund? Web site. To search the database, you'll need your Social Security number and the exact amount of the refund. If you would rather talk to a person, call the IRS refund hotline at 800-829-1040.
The IRS also may owe you money if you held a job in the past few years, but made too little money to have to file a tax return. For tax year 2013, the minimum income requirement was $10,000 for a single filer and $20,000 for married filing jointly. Even if you made less than that, though, your employer probably withheld taxes from each paycheck. To get this money, you must file an income tax return within three years of the return due date [source: IRS].