Supplementary Budget Act IV for 2025 was passed by the Icelandic Parliament on December 18, 2025. The law makes changes to the 2025 budget by modifying state treasury expenditure authorizations and reallocating funds between state budget items. This is the fourth supplementary budget for 2025 and provides for adjustments to the state's financial plan due to changed circumstances or new needs that arose during the year. The law affects state treasury expenditures and thereby the services and operations provided by the government.