Finland's current constitutional provisions are enshrined in a single statute: the Constitution of Finland (731/1999).
Before the enshrinement, the Finnish constitutional provisions were divided between four separate statutes, which all had a constitutional status; the Constitution Act of 1919 (Finnish: Suomen hallitusmuoto), Parliament Act of 1928 (Finnish: valtiopäiväjärjestys), the Ministerial Responsibility Act of 1922 (Finnish: laki eduskunnan oikeudesta tarkastaa valtioneuvoston jäsenten ja oikeuskanslerin sekä eduskunnan oikeusasiamiehen virkatointen lainmukaisuutta, short title ministerivastuulaki) and the Act on the High Court of Impeachment of 1922 (Finnish: laki valtakunnanoikeudesta). All these statutes were merged into a single constitution and repealed with the passage thereof.:§131
The fundamental principles of the Constitution Act of 1919 and the Parliament Act of 1906, amended in 1928, remained unchanged during the first fifty years of Finnish independence, as there was little pressure or need for any amendments to the Constitution Act. However, this did not prevent the Constitution from adapting to the changing needs of the day. The flexibility of the Finnish Constitution is due to the use of "exceptive laws," a distinctive feature of the Finnish system: instead of amending or changing the Constitution, an act may be passed as an ad hoc exception to it. Such an exceptive law does not become part of the Constitution and it may be repealed like an ordinary act. Exceptive laws were formerly much used, even to the point of threatening to undermine respect for Constitutional provisions. Today, their use is limited.
The first major constitutional reform came in 1983, with the re-writing of many important provisions governing parliamentary procedure, mostly in the Parliament Act. However, the most extensive and important reforms came in 1987, when provisions on the holding of consultative referendums were added to the Constitution. The indirect form of electing the President of the Republic via an Electoral College was replaced by a system which combined the Electoral College with direct election, and the provisions governing the postponement of ordinary legislation were amended by shortening the period for which a bill could be postponed.
In 1991, the direct popular election of the President was introduced, with provision for a second ballot where necessary. The new system was used for the first time in 1994. The President's term of office was also limited to two consecutive terms of six years, and the President’s powers were limited in that he or she could henceforth only dissolve Parliament on receipt of a reasoned request from the Prime Minister and having first consulted the Speaker and the party groups in Parliament. The 1991 reform also amended the provisions in the Constitution Act and the Parliament Act relating to State finances.