24 February 2012
The last Alpha charactor of the PAN is a check digit ( or in this case a check alpha). This helps in tracking or identifying PAN's which are written wrongly either intentionally or by mistake. for Eg. the next pan after the one given by you in example is AAACP1235? Imagine if the last alpha were not there, then anybody can guess the sequence of pan's given a particular pan. If the Name condition and status condition matches anybody can give a fake PAN based on a valid pan they may come across. the Last letter P prevents this. This letter is a random alphabet added.so the PAN can be AAACP1235Q or AAACP1235B. Hope this is clear.