Regulation 5 Marking of notices and documents
Any notice or other document which is to be served on a person as having an interest in premises, or on a person as an occupier of premises, in the manner provided by section 51(2)(b) of the Act shall, at the beginning of that notice or other document, have clearly and legibly marked upon it, in the following form, the words:
IMPORTANT—THIS COMMUNICATION AFFECTS YOUR PROPERTY
and where such notice or other document is not sent in a pre-paid registered letter or by the recorded delivery service but is delivered under cover to some person on the premises (in accordance with the said section) the cover shall also be marked in like manner.