Abbr. CD. A certificate of deposit is a money market instrument and negotiable claim issued by a bank in return for a short- to medium-term deposit usually lasting 1-12 months, but in exceptional cases up to 5 years. By issuing the certificate the bank confirms that it has received a certain sum and that it will repay this amount to the lender together with the interest due at the end of the period decided upon by the lender. Normally certificates of deposit are issued in US dollars, even if they are issued by US banks through their branches in London (London CDs). Those certificates issued in New York play an important role as money market paper.