Belgium - 1989 Party Finance Law

Title Article 23
Chapter CHAPTER IV The accounts of political parties
Article

23

The management board of the institution referred to in Article 22 shall designate an auditor.
Said auditor shall prepare an annual financial report on the registered accounts and closure of revenues and expenditure of the institution, as well as ¬the revenues and expenditure of the political party.

Source http://www.ejustice.just.fgov.be/cgi_wet/wet.pl