In Sweden there are two kinds of referendums that apply to the entire country: consultative referendums and constitutional referendums.
The Riksdag determines whether a national referendum is to be held, as well as who is entitled to vote and which alternative responses are to be presented.
National referendums are basically subject to the same rules as parliamentary elections with regard to electoral districts and voting inside and outside Sweden etc.
A referendum held in one municipality or county council is always consultative. The municipalities and county councils themselves determine if and when such referendums are to be held.