A range of entities, including limited liability companies, housing or real estate companies, associations, foundations, municipalities, and foreign corporations are required to file their corporate tax returns within the deadline.
Finland’s Tax Administration has reminded taxpayers, on 2 April 2026, of the approaching deadline for submitting corporate tax returns for accounting periods ending in December 2025, with filings due by 30 April 2026.
A range of entities, including limited liability companies, housing or real estate companies, associations, foundations, municipalities, and foreign corporations are required to file their corporate tax returns.
Taxpayers can submit the tax return and the necessary attachments in MyTax. Alternatively, taxpayers can send them as a file in the Ilmoitin.fi service or through a software interface (in Finnish and Swedish, link to Finnish).
Tax return of limited liability companies and cooperative societies
Companies with taxable income, expenses, assets, property, debt, or other tax-relevant transactions during a given tax year are required to file an income tax return using Form 6B. This obligation remains in effect even if the company or cooperative was inactive during the tax year or has been declared bankrupt.
Filing is also mandatory when the Tax Administration has issued a directive instructing the company to do so. In cases where a company has multiple accounting periods ending within the same calendar year, a separate set of tax return forms must be completed for each period. The Tax Administration will subsequently consolidate the data from all submitted periods.
Instructions for filling in Form 6B (Limited liability companies and cooperative societies)
This provides a comprehensive guide for completing Form 6B, the income tax return for limited liability companies and cooperative societies (tax years 2024–2025). It covers key sections including basic company details, shareholder information, taxable income calculations, net worth calculations, and financial statements. Notable updates include a new extra R&D additional deduction available from 2024 (based on year-over-year R&D expense growth), and the elimination of the employer training deduction from 2025. The guide also covers non-deductible costs, depreciation rules, agricultural income, international operations, and how to make corrections.
Tax returns for Foreign corporations
Foreign corporate entities operating in Finland may be subject to income tax obligations if their activities give rise to a permanent establishment in the country. A permanent establishment is defined as a fixed place of business through which an enterprise’s operations are carried out, and may include a branch, factory, natural resource extraction site, a long-term construction project, or a dependent agent. Where a permanent establishment exists, the foreign company becomes liable to pay Finnish income tax on all income attributable to it. Foreign corporate entities are advised to evaluate whether their operations in Finland meet this threshold.
Instructions for filling in Form 6U (Foreign corporations)
This provides Finland’s Tax Administration instructions for completing Form 6U — the income tax return for non-resident foreign corporate entities operating in Finland for tax years 2025 and 2026. It covers how to report business income, deductible costs, depreciation, financial expenses, assets, and liabilities. Key 2025/2026 updates include the removal of the employer training deduction, the end of increased machinery depreciation, and new rules on labour union membership fee deductibility. The guide also explains permanent establishment rules, R&D additional deductions, transfer pricing requirements, shareholder reporting, net worth calculations, and the impact of ownership changes on loss deductions.
The 6C income tax return is a designated filing form for specific organisations in Finland, applicable for the 2025 and 2026 tax years. The entities required to file include associations, foundations, municipalities, major churches and registered religious communities, student unions, polytechnics and universities, reindeer grazing associations, and welfare areas. The form’s instructions specify exactly what financial information each of these organisations must report to fulfil their tax obligations.
Instructions for filling in Form 6C (Associations and foundations)
This provides instructions for completing the income tax return form 6C, applicable to associations, foundations, municipalities, parishes, universities, student unions, and welfare regions. It covers how to report basic organisation details, distinguish between tax-exempt and taxable income (such as business income and property income), and how to calculate taxable results. It also explains required attachments like financial statements, notes a key 2026 change where organisations can no longer deduct trade union membership fees from business income, and outlines how to correct or amend a submitted tax return.
