Traditional certificate based cryptosystem requires high maintenance cost for certificate management. Although, identity based cryptosystem reduces the overhead of certificate management, it suffers from the drawback of key escrow. Certificateless cryptosystem combines the advantages of both certificate based and identity based cryptosystems as it avoids the usage of certificates and does not suffer from key escrow. In this paper, we propose a pairing based certificateless signature scheme that is efficient than the existing scheme.