Dual mandates in Belgium: who can hold what

Cumul des mandats means holding several elected or public offices at the same time, for example MP and mayor. In Belgium the rule is not the same everywhere: no ban in the Chamber, a partial ban in the Walloon Parliament, and a full ban in the Brussels Parliament since December 2024.

Dual mandates: three regimes and one shared cap

The term "décumul" (the ban or limit on holding several offices) covers several systems here that do not overlap. First separate two questions the press often mixes up. The first: can a member of parliament also hold a local executive office? The second: how much can they receive in total?

The first question belongs to each assembly. The second belongs to an income cap, the "150% rule", explained further down.

The Flemish line deserves a caveat: it rests on a 2022 press article, not on a Flemish text I was able to consult. I have not checked whether the rule has changed since.

Federal level: little décumul, a ministerial incompatibility

At federal level, the law of 6 August 1931 sets the incompatibilities of members of parliament. The law of 4 May 1999 limits the number of paid executive offices to one. Since the constitutional revision of 5 May 1993, a federal minister can no longer sit in parliament. These landmarks come from the CRISP Courrier hebdomadaire (2015).

Seven décumul bills were tabled in the Chamber between 2010 and 2012. All lapsed on 28 April 2014, at the end of the term.

So no general ban. The income cap acts as the safeguard.

Wallonia: a quarter of exceptions per group

The special decree of 9 December 2010, published in the Moniteur belge on 22 December 2010, forbids a Walloon MP from also being mayor, alderman or CPAS chair. It provides one exception: a quarter of the members of each political group may hold both. They are chosen by their electoral penetration rate, meaning the votes they won relative to the number of voters in their constituency.

A transition period ran from 2014. In October 2016, RTBF counted 32 of 75 Walloon MPs who had to choose, over 40% of the assembly. In November 2016, according to La Libre and L'Avenir, party presidents discussed repealing the decree, then backed off.

After the regional elections of June 2024, La Libre recalled the mechanism: the one-quarter quota is calculated on each candidate's penetration rate in the regional vote, not the municipal one. Small constituencies, with fewer seats, make that rate easier to reach, which lets some elected officials get around the ban, the same paper noted in January 2024.

Brussels: from the failed 2018 vote to the full ban of 2024

On 8 June 2018, the Brussels Parliament voted on a full décumul. The French-speaking group approved it by 58 votes to 12, with 3 abstentions. The Dutch-speaking group rejected it by 11 votes to 6. As a majority was required in each language group, the text fell.

A new vote followed after a thirty-day period, by simple majority. On 14 June 2022, the Interior committee approved the full-décumul ordinance, with entry into force planned for 2024.

It has applied since December 2024, after the municipal elections of 13 October 2024. According to RTBF on 18 November 2024, no one can be both a member of parliament (regional, community, federal or European) and mayor, alderman or CPAS chair. The status of "bourgmestre empêché" (a mayor who steps aside to keep another office) no longer exists in Brussels. In 2022 the press counted nine elected officials affected; in 2024, five mayors elected to parliament in June had to choose.

According to La Libre (2022), a member of the municipal executive may keep a seat as an ordinary councillor.

Income cap: the 150% rule and how it is calculated

The cap does not depend on the assembly, at least in principle: an office-holder's public income may not exceed 150% of the federal parliamentary allowance. A bill tabled in the Chamber on 29 November 2017 (DOC 54 2811/001) summarises the existing rule as follows: additional public income is limited to half the parliamentary allowance, so 150% in total. That text aimed to extend the rule to fees from boards of inter-municipal bodies and public organisations. I have not checked whether it was adopted.

The most recent figure comes from Brussels. According to La DH on 25 March 2024, the cap stood at 228,163.89 euros in 2024. Worked backwards, that gives a reference allowance of about 152,109 euros. Excess pay can be reduced, but not below 63,648.29 euros, according to the Brussels Parliament's transparency unit.

Oversight is Brussels-based too: that unit and an ethics committee, set up in March 2024, examine individual situations. La DH documented in March 2024 cases of excess in one Brussels municipality; in one of them, the transparency unit judged the rules had been respected despite a total above 150%, which shows the method of calculation is open to debate. For the base pay of each office, see the article on the salary of a minister, an MP and a mayor.

Why limit dual mandates? Why defend them?

Geoffrey Grandjean, of the University of Liège, listed the arguments in the CRISP Courrier hebdomadaire in 2015. I give them as he attributes them, without taking sides.

For limiting:

• Availability: one more mandate leaves less time for the parliamentary one, an argument attributed to French researchers cited by the author.
• Renewal: according to political scientist Yves Mény, holding several offices slows the arrival of new elected officials.
• Separation of powers: some authors fear the legislature's dependence on the executive.
• General interest: article 42 of the Constitution says members of both Chambers "represent the nation, and not only those who elected them".

Against limiting:

• Proximity: work on the "mayor effect" shows citizens tolerate multiple offices better when it concerns the mayor of their own municipality.
• Local experience: one cited study finds a slightly positive effect of holding several offices on parliamentary activity, and notes that a simple ban can provoke workarounds.
• Limited evidence: another researcher finds no clear net effect on activity.
• Autonomy: the committee of the German-speaking Community rejected a décumul proposal on 18 October 2010, citing local experience and freedom to organise working time.

Most of the studies cited concern France. They inform the debate without settling it for Belgium.

How many offices did a Belgian elected official hold?

The Cumuleo tool, cited in the same CRISP issue, estimated in 2014 that Belgian representatives held on average five to eight paid offices, all types included (board seats too). It is an old snapshot, from before the Brussels rules of 2024.

Above all it shows the scale of the phenomenon that the income cap and the décumul rules try to frame.

Dual mandates, financing, pay: how do they fit together?

Holding several offices is only one piece of oversight of elected officials. It is read alongside the rules on financing of political parties, alongside the powers of each entity, and alongside the declarations of mandates that elected officials must file with the assemblies.

None of the rules set out here says which position is the right one. Party positions on institutions can be read, without ranking, in the institutions comparison and in the comparator; thematic scores reflect a position on an axis, not a quality, as the methodology explains.

Sources: CRISP Courrier hebdomadaire, "La limitation du cumul de mandats par les députés wallons", 2015, text by Geoffrey Grandjean (open-access version); Chamber of Representatives, bill DOC 54 2811/001, 29 November 2017; BX1, 8 June 2018 vote on Brussels décumul; RTBF, full décumul in Brussels, 14 June 2022 and officials' choices, 18 November 2024; La Libre, June 2022, 26 January 2024 and 16 October 2024; La DH, income cap, 25 March 2024.