By Tami Luhby

NEW YORK (CNNMoney.com) -- If your bank contacts you about a bond-like investment you made some time ago, don't ignore it. You could benefit from an unusual settlement that will allow you to get back 100% of your investment's value.

Citigroup announced Thursday that by Nov. 5 it would buy back so-called auction-rate securities from individual investors, charities and businesses with assets of $10 million or less. Hours later, Merrill Lynch (ML) announced...