Municipal bonds are often "advance refunded." Bonds that are not yet callable are defeased by creating a trust that pays the interest up to the call date, and pays the call price. New debt, generally at lower interest rates, is issued to fund the trust. Issuing new securities generally has zero...

Build America Bonds (BABs) were issued by municipalities for 20 months as a part of the 2009 fiscal package. Unlike traditional tax-exempt municipals, BABs are taxable to the holder, but the Treasury rebates 35% of the coupon to the issuer. The stated purpose was to provide municipalities access...