Was worth asking! Thanks for all the comments.

Agreed. But why quote the law and state an offence code? If it's just an envelope.

There is also a bit above that, with two boxes called "Offence", to the right of "Time" with 12 written in there.

Thanks! Here it is: http://i279.photobucket.com/albums/kk136/captquo/Scan3.jpg

I would upload an image of the envelope, but I don't know where I can . . . It says "PENALTY CHARGE NOTICE (ENCLOSED)" on the envelope. But before that it says "It is a Criminal Offence to Interfere with this Notice" suggesting that the envelope is the notice? But this contradicts the enclosed statement.

I received a PCN from the London Borough of Merton as my residents permit had expired. The PCN seems to be worded correctly. However, the envelope for the notice has a little box called "offence". The code is 12. On the notice this is referred to as the "contravention code" - also 12. My question is, does the envelope constitute part of the PCN? If so, then is the ticket invalid as they used the word "offence"? Thanks.