The debentures carry a fixed (coupon / rate of interest, the payment of which is legally binding enforceable. The debenture interest is tax-deductible and is payable annually, semi-annually quarterly. Some public sector undertakings issue tax-free bonds that, income from which is from tax in the hands on the investors. A company is free to choose the coupon rate which may be fixed or floated, being determined in relation to some benchmark rate. It is also related to the credit rating of the debenture as an instrument.