Issues in relation to which referendums are optional at the national level

Bulgaria
Bulgaria, Act on Direct Participation of Citizens in Government and Local Government of 29 May 2009 (as amended in 22 February 2022), accessed 7 September 2022
Art. 9. (1) (Amend. - SG No. 56 of 2015, in force from 24.07.2015) A national referendum shall be held for direct resolution by the citizens of issues of national importance within the competence of the National Assembly.
(2) Questions may not be resolved through a national referendum:
1. (repealed - SG No. 88 of 2020)
2. under Art. 84, items 4, 6, 7, 8, 10, 12, 16 and 17, art. 91, 91a, Art. 103, para. 2, Art. 130, para. 3, Art. 132a and Art. 147, para. 1 of the Constitution;
3. for the amount of taxes, fees and labor and insurance payments and contributions;
4. of the state budget;
5. of the rules of the internal organization and activity of the National Assembly.
(3) Codes and laws that completely regulate the matter in a given area cannot be submitted to a referendum in their entirety.
(4) A referendum on issues regulated in international treaties concluded by the Republic of Bulgaria may be held before their ratification.
(5) When holding a national referendum, one or more questions may be voted on.
(6) The decision adopted by a national referendum is not subject to subsequent approval by the National Assembly. The National Assembly adopts an act when it is necessary to implement the decision.
(7) If, within three months after the announcement of the result of the referendum, the National Assembly does not bring its act into line with the will expressed by the voters, this act shall not be applied in the part that contradicts the decision of the referendum.