(MONEY Magazine) -- The U.S. government is making a mint off of birthdays, bar mitzvahs and graduations: About $13 billion in savings bonds have matured but not yet been redeemed.

If you own one of them, you aren't earning a penny in interest on your money.

At treasurydirect.gov, you can search for missing bonds or calculate the value of your bond and find out if it's paying interest; typically, if your bond was issued before December 1965, the interest meter ran out after 40 years; most bonds issued after that pay out for 30 years.

No bond is too old to cash in. Simply head down to your bank with your bond and photo ID. Yes, you will likely owe federal tax on the payout (using it for college may give you a break), but that's no reason to leave your asset sitting in the U.S. Treasury earning nada for you.

"You are essentially losing money the longer you hold, due to inflation," notes Stephen Meyerhardt, a spokesman for the Bureau of Public Debt. "You can be doing a lot better if you cash in, pay the tax, and reinvest it in something actually earning interest." (And hey - your bond is exempt from state tax.)

1. Cash in old savings bonds

2. Boost your savings rate

3. Stop paying for unneeded life insurance

4. Consolidate your retirement accounts

5. Prune your credit cards

6. Unload unused gift cards

7. Finally sell that lousy investment