Biometrics has been widely recognised as a powerful tool for problems requiring personal identification. Unlike traditional authentication methods, however, biometrics-based authentication systems may reject valid users or accept impostors. The accuracy of a biometric system could be defined as its combined ability to reject impostors and accept valid users. The biometrics industry places heavy emphasis on security issues relating to the rejection of impostors while denial of access remains largely neglected in the evaluation of biometric systems. In this paper, we discuss how denial of access may impact on all major aspects of a biometric system and propose solutions to reduce the probability of denial of access based on more sophisticated authentication decision-making strategies.