Finnish limited company tax return (Form 6B): deadline and checklist

Karma Accounts · Published 19 October 2026

A Finnish limited company (osakeyhtiö, Oy) files its tax return on Form 6B within four months of the end of the last calendar month of its financial year: for a year ending on 31 December 2026, by 30 April 2027. It is filed electronically with the financial statements attached whenever the company had income, expenses, assets, debts or other information affecting tax, which the Tax Administration says includes a year with no activity. The company pays 20 % income tax on its taxable profit, not on its turnover. An accountant can prepare and file the return, but the board stays responsible for it.

The Oy tax return at a glance

Question	Answer
Form	6B, business tax return for corporate entities
Deadline	4 months from the end of the financial year's last calendar month
How	MyTax (OmaVero), Ilmoitin.fi or accounting software
Attachments	the financial statements, and the auditor's report if audited
Tax rate	20 % of taxable income
Filed late or wrong	usually a 100 euro late filing fee if filed before the assessment ends; a tax increase may follow if not filed by then or for errors

Who has to file

An Oy files Form 6B if it had any income, expenses, assets, liabilities or other information affecting tax in the tax year, the Tax Administration (Verohallinto) says, including a year with no activity, and always when the Tax Administration asks for one. If two financial years end in the same calendar year, each gets its own return and both belong to the same tax year. The board is responsible for filing (Act on Assessment Procedure, VML 9 §), even when an accountant does the work.

The deadline

Financial year ends	Form 6B due
31 December 2026	30 April 2027
15 July 2026	30 November 2026

If the last day falls on a Saturday, Sunday or public holiday, the return may be filed on the next business day. An extension is granted only for a special reason, such as illness, and must be requested before the deadline, in MyTax or on paper form 3105, one company per request. Paper Form 6B is allowed only when electronic filing is not possible for a special reason, such as a technical fault.

What goes with the return

According to the Tax Administration, a company filing Form 6B attaches:

the income statement and balance sheet with comparatives, without the balance sheet specifications
the notes, without their specifications
the auditor's report, if the company is audited
the general meeting's decisions: when the statements were adopted, how the profit or loss was dealt with, and any dividend with its amount and payment date
the report of the board and a cash flow statement, if the company must prepare them

Named with the right attachment types, they are passed on to the Finnish Patent and Registration Office (PRH) for the Trade Register, which takes only adopted statements. If the general meeting comes after the tax deadline, attach the statements without choosing them for PRH and supplement the return electronically after the meeting: the Tax Administration forwards statements to PRH if they arrive within 10 months of the end of the tax year, or within 15 months of the end of the financial year through MyTax's financial statements and dividend function. A dividend decided after the return is filed is reported within one month of the decision, and an auditor's report finished after the deadline within one month of the audit. The timetable is in financial statements deadlines and the work in order in year-end steps.

What to give your accountant for the tax return

The return is built from the closed books. Collect:

Bank statements and closing balances for every account, including payment services and foreign accounts.
Loans: year-end balances and interest paid.
Shareholder loans and anything else owed between you and the company. Form 6B lists them per shareholder; see shareholder loans.
Dividends decided or planned, with the meeting's minutes; see salary or dividends.
Assets bought or sold: invoices for equipment, computers and vehicles, for the depreciation.
An inventory count on the last day, if you hold stock.
Unpaid invoices both ways at the year end.
The owner's salary and benefits, such as a phone, meals or a company-owned home the owner lives in.
Cars: who owns each one, any car benefit, and the mileage log for a private car used in the business.
Other payments to shareholders: rent, interest, or anything the company bought from them.
Foreign income and foreign tax withheld.
Prepayments paid, including any additional prepayment.
Last year's return and tax decision, which show confirmed losses.
Ownership changes during the year, which can cancel past losses.

What the board and managing director approve and sign

These stay with the company's officers. Every Oy has a board; a managing director is optional (OYL 6:1).

Oversight. The board makes sure the supervision of the accounts is properly arranged, and the managing director, if there is one, that the bookkeeping complies with the law (Limited Liability Companies Act, OYL 6:2 and 6:17).
The financial statements. Prepared within four months, then dated and signed by the board and the managing director (Accounting Act, KPL 3:6 and 3:7).
Profit and dividend. The annual general meeting, within six months of the year end, adopts the statements and decides on the profit (OYL 5:3). It can normally distribute no more than the board proposes or approves, with exceptions such as a minority dividend demand (OYL 13:6 and 13:7). No dividend may be paid if the company is, or would become, unable to pay its debts (OYL 13:2). See our AGM minutes template.
Access. The company arranges a Suomi.fi mandate for the accountant. The managing director or another person entitled to represent the company alone can grant it alone; otherwise the persons entitled to represent it grant it together. Here is how to approve our request.
The return. Read the draft before it is filed: the board answers for the figures.

How the 20 % is worked out

The rate is 20 % (Income Tax Act, TVL 124 §) of taxable income: the accounting profit adjusted under the Business Income Tax Act (EVL). Only 50 % of entertainment expenses is deductible (EVL 8 §); fines and the late filing fee are not deductible (EVL 16 §, VML 33 §); and from tax year 2026, neither are membership fees of organisations with labour market objectives (act 1145/2025).

A tax loss is confirmed by the Tax Administration and deducted automatically from the profits of the next 10 tax years (TVL 119 §). It is lost if more than half of the shares change owners during or after the loss year, other than by inheritance or will, unless the Tax Administration grants permission on application (TVL 122 §).

The government proposal HE 151/2026, given to Parliament on 3 September 2026, would cut the rate to 18 % from tax year 2027 and let losses from tax year 2026 onwards be deducted for 25 years. The current 20 % rate and 10-year rule apply until the change is enacted; the Tax Administration's website shows whether it has been.

Paying the tax

The tax is paid during the year as prepayments, based on the latest assessment or, for a new company, its own estimate; see tax prepayment. If they fall short:

Additional prepayment (lisäennakko). A company can request one only after its tax year has ended, and pays no interest if it pays within one month of the end of the tax year. The minimum is 500 euros.
Residual tax (jäännösvero). Anything still unpaid is charged after the assessment and falls due on the 3rd day of the second month after the month the assessment ends. Reduced late payment interest runs on it from the first day of the second month after the tax year ended until the due date; the rate is 4.5 % in 2026, and 20 euros is deducted from the interest calculated, at most the amount of the interest.
Paid late. Residual tax paid after its due date carries late payment interest, 9.5 % in 2026.

When the assessment ends and what lateness costs

The assessment ends on the date on the tax decision, at the latest 10 months after the end of the financial year's last month (VML 49 §): for a year ending on 31 December 2026, by 31 October 2027.

Filed late, or corrected on your own initiative, before the assessment ends: a late filing fee of 100 euros for a company instead of a tax increase, once per tax year (VML 33 §). A correction normally triggers it only if it increases taxable income. It is not charged for a valid reason, a minor omission, or one beyond the company's control.
Not filed before the assessment ends, or income left out or wrong: a tax increase of 2 % of the added income, 3–10 % if the neglect is repeated or shows plain disregard for tax obligations, and at least 150 euros for a company (VML 32 a §). If you ask for a correction yourself after the assessment has ended and have explained the matter, the increase is 0.5 %.

Outsourcing an Oy's bookkeeping and tax return

When you compare accounting firms, ask whether the monthly fee includes the financial statements and the tax return, and when you will see the draft. Our accounting cost guide shows what firms charge and what is often billed separately.

What we do

We keep the books every month, prepare the financial statements, and file Form 6B with the attachments named so they reach the Trade Register, after you have approved the draft. Before the year closes, we tell you whether an additional prepayment would save interest. Our limited company accounting is 199 euros a month up to 240 000 euros of turnover and 249 euros up to 500 000 euros, with a written quote above that, plus VAT 25.5 %. The Oy price includes the financial statements and the tax return, the VAT returns and the software, with no limit on receipts. We work in English, Finnish or Hindi. See the price list or request a quote.

Frequently asked questions

When is the Oy tax return due?

Within four months of the end of the last calendar month of the financial year. For a year ending on 31 December 2026, the deadline is 30 April 2027.

Does an inactive Oy have to file a tax return?

Yes, if it had any income, expenses, assets, debts or other information affecting tax. The Tax Administration says this applies even when the company had no activity, and the financial statements still go to the Trade Register.

Who files the company tax return?

The board is legally responsible (VML 9 §). An accountant can prepare Form 6B and file it in MyTax with a Suomi.fi mandate from the company, once the company has approved the figures.

I want to outsource bookkeeping and tax returns for my Finnish limited company, which accounting firm should I contact?

Compare written yearly quotes covering bookkeeping, VAT returns, the financial statements and the tax return. We do all of it for 199 euros a month plus VAT up to 240 000 euros of turnover, year-end included, in English, Finnish or Hindi.

Sources

Please note: this is general information about Finnish rules, not advice for your own situation, and the rules change. Ask us before you act on it.

Your Oy's books and year-end

Bookkeeping, VAT, the financial statements and the tax return for 199 € a month plus VAT up to 240 000 € of turnover, 249 € up to 500 000 € and a written quote above that. See accounting for limited companies.

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