It is already known that the internal permutation of the stream cipher RC4 generally deviates from a random permutation. These deviations are termed as biases, theoretical justification of which is being reported since early 2000. However, there are several biases (anomalies), which are not proven till date. In this study, the authors provide the theoretical proofs of all significant anomalies of RC4 in the 16-byte key setting. In the process, they also provide the theoretical justification of the zig-zag type distribution of the 31st output byte of RC4 (first discovered and presented by AlFardan et al. in USENIX 2013). © The Institution of Engineering and Technology 2016.