When a security is listed for trading, but the physical certificate has not been issued yet, it is known as when-issued trading. This is common when a new security is introduced to the market. The exchange bulletin will specify if the trading will be done on a when-issued basis. The delay in issuing the certificate is usually due to logistical reasons. Despite the delay, the issuance of the security is guaranteed and the trading period is typically less than one week.
