FRED has added 38 historical commercial paper (CP) series from before April 2006: On April 10, 2006, the Federal Reserve Board made major changes to its CP outstanding calculations. New outstanding categories were added, some existing category definitions were modified, and current and historical CP issuer information was updated. For more information, refer to the Commercial Paper Rates and Outstanding Summary.
CP consists of short-term, promissory notes issued primarily by corporations (up to 270 days in maturity but averaging about 30 days). CP is often used to raise cash for current transactions as a lower-cost alternative to bank loans.