The National Archives holds around 210 shelf-kilometres of records dating from the Middle Ages to the present day. The oldest document, a letter of protection given by King Birger to the women of Karelia, dates from 1316. The oldest continuous series of records, the accounts of the bailiffs (voudintilit), begin at the end of the 1530s.
There are also series of accounts of the provincial administration, court records and land survey maps dating from the period when Finland was a part of the kingdom of Sweden. The most important sources from the period of autonomy are the large archives of the Senate, the State Secretariat and the Chancery of the Governor-General.
The National Archives accepts records older than 40 years to be stored permanently from state and central government agencies as well as district and local authorities operating in the Helsinki region. Around 10–15 per cent of the records of the public authorities are stored permanently.
The National Archives also acquires private archives as donations or deposits. Private archives include papers of statesmen, politicians, influential people in society and culture as well as of ordinary citizens and different organisations.
The copy collections are comprehensive and popular, especially the General List of Settlement in Finland and copies of historical parish records used by genealogists. In addition, the National Archives has copies on microfilm of the records stored in parish archives as well as foreign archives.
The archival records older than about the turn of the 20th century of all Evangelical-Lutheran parishes in Finland are available on microfilm in the National Archives.
Furthermore, the National Archives has a considerable number of maps and drawings, the oldest of which date from the 1650s. Computer data has also been transferred to the National Archives, the most comprehensive of which is the material transferred by the Population Register Centre.
The Hallituskatu Office of the National Archives preserves documentary material of every ministry, excluding the Ministry for Foreign Affairs, the Ministry of Defence and the Prime Minister's Office. Most of the material has been entered into the Vakka database. The documents of committees, consultative committees, boards, commissions, working groups and other projects in operation in 1998 and ever since have been registered in the HARE project register of the Finnish Government and filed in project archives by project. Queries for the archives of committees, consultative committees, boards, commissions and working groups in operation before 1998 should be made directly to the Officer on duty in the Hallituskatu Office.
The following archives in the custody of the National Archives are worth mentioning separately:
- Transcribed records of the lower courts of justice from the 17th century
- The archives of the Imperial Senate 1809–1918
- The archives of central administrative boards from the beginning of the 19th century
- Supreme court archives since 1918
- The archives of Porvoo Cathedral Chapter and several parishes in the Province of Uusimaa
- The archives of the Defence Forces since 1918
- Records from the war years 1939–1945
- The archives of all of Finland’s presidents except those of Urho Kekkonen and Martti Ahtisaari
- The archives of the provincial government of Uusimaa from the 17th century
- Archives of district and local authorities in the Province of Uusimaa
- Government and ministerial archives dating back to 1918
- The archives of the State Secretariat and the Chancery of the Governor-General 1809–1918
- Archives of the judicial administration in Old Finland, which belonged to the Russian empire in 1721–1812
- Russian military records 1722–1918
- Accounts of bailiffs and administrative provinces 1537–1808
- Military records prior to 1809