The Party Wall Act: 1996 came into force on 1 July 1997 and applies throughout England and Wales.
The Act covers various work that is going to be carried out directly to an existing party wall or structure, a new building at or astride the boundary line between properties and excavation within 3 or 6 metres of a neighbouring building(s) or structure(s), depending on the depth of the hole or proposed foundations.
The key point is whether your planned work might have consequences for the structural strength and support functions of the party wall as a whole, or cause damage to the Adjoining Owner’s side of the wall.
If you are in doubt about whether your planned work requires a notice you should seek advice from Building Control.
Further information is available on the Planning Portal website where you can find an Explanatory Booklet