Treasury Bill

With the Treasury Bills, the Bank acts as an intermediary and purchases government securities on behalf of customers.
Government Bonds purchased are another form of security and such investments may be retired or rolled over on the date of maturity depending on what the customer wants.

With the 91 and 182-day bills, interest can be discounted up front and the bill again rediscounted before maturity (i.e. it can be redeemed before maturity).