A dividing fence is a fence that separates the land of different owners whether the fence is on the common boundary of adjoining lands or on a line other than the common boundary. A dividing fence does not include a retaining wall.

If your neighbour does not agree to the fence, you need to obtain a quotation and send them a Dividing Fences notice. They have the option to respond, but if they don’t, you may go ahead and organise for the fence construction and your neighbour will have to meet their share of the cost. If there is a genuine dispute, you may try to settle it through a Community Justice Centre or, failing that, take the matter to the Local Court.
A list of dispute resolution services are available at; http://www.alldayfencing.com.au.

Avoid Disputes! Download letters to send your neighbours, http://www.alldayfencing.com.au/adfcouncil.php