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Change financial year in Finland: the 18-month rule and the steps

Karma Accounts · Published 2 November 2026

To change the financial year (tilikausi) of a Finnish limited company (Oy), the general meeting decides the new year and the company files a change notification in the YTJ service. The change takes effect only when the Finnish Patent and Registration Office (PRH) registers it, and it cannot be backdated. The year in between can be shorter or longer than 12 months, but never more than 18. PRH charges 55 euros, or 355 euros if the financial year is written in the articles of association. The company tax return is then due four months after the end of the new year's last calendar month.

How long a financial year can be

Under the Accounting Act (kirjanpitolaki) 1:4 a financial year is 12 months. When a business starts or stops, or the year end is moved, it can be shorter or longer, but at most 18 months. So a change creates one transitional year, shortened or lengthened; if lengthening would pass 18 months, you shorten.

The first financial year

A new Oy sets its financial year in the founding agreement or the articles of association (Limited Liability Companies Act, osakeyhtiölaki, OYL 8:4). The first year can also be shorter or longer than 12 months, up to 18. A company founded in October 2026 can, for example, end its first year on 31 December 2027 and file one set of financial statements for those 15 months.

The tax year is made of the financial years that ended during the calendar year (Act on Assessment Procedure, verotusmenettelylaki, section 3), so this company's first tax return is for 2027.

Why companies change their year

• A seasonal business. A ski rental or a summer café is easier to close after the season, when the stock is counted.
• A group. Group companies are easier to consolidate when they share one year end.
• A foreign parent. A Finnish subsidiary often follows its parent's year, for example 1 April to 31 March.

Who decides in a limited company

The general meeting always decides, even when the financial year is not in the articles (OYL 8:4); the board cannot.

• The year is in the articles. The change is an amendment of the articles, which needs at least two thirds of the votes cast and of the shares represented at the meeting (OYL 5:27). PRH charges 300 euros for the articles plus 55 euros for the financial year, 355 euros in all.
• The year is only in the founding agreement. An ordinary general meeting decision is enough. PRH charges 55 euros.

A sole owner can decide without a meeting, and so can all shareholders if they agree unanimously. The decision is written down, dated, numbered and signed; if there is more than one shareholder, at least two of them sign it (OYL 5:1).

Registering the change with PRH and the Tax Administration

1. Decide. One decision sets both the transitional year and the new year, for example "the current financial year ends on 30 June 2028; from then on it is 1 July to 30 June".
2. Notify in YTJ. A board member or the managing director signs the notification; a procuration is not enough, but they can authorise someone else in YTJ. Attach a copy or extract of the minutes certified by one person, and the new articles if they were rewritten in full. From 1 January 2026 limited companies must file Trade Register notifications electronically.
3. One notice is enough. The YTJ notification goes to both the Trade Register and the Tax Administration.
4. Watch the timing. To lengthen, notify two months before the registered year ends; to shorten, two months before the new, shorter year ends. PRH must have registered the change before that year end, so check PRH's processing times and file early.

The other company changes and their fees are in our article on changing company details at PRH.

A sole trader's financial year

For a sole trader (toiminimi) the financial year is always the calendar year (Accounting Act 1:4). The exception is a toiminimi that keeps double-entry books: it can choose another 12-month year and change it under the same 18-month rule. On single-entry books you cannot change the year without moving to double-entry bookkeeping first.

A sole trader also notifies the change in YTJ, with the same two-month notice, and may still file on paper. The change is not entered in the Trade Register, so there is no PRH fee; it takes effect once the Tax Administration has processed the notice, and it cannot be backdated. The income is taxed in the year in which the financial year ends, and all financial years that ended in a calendar year go on one business tax return (Form 5), due by the spring deadline in MyTax (1 April 2026 for 2025).

What changes in tax and filing

Tax year. A long transitional year can leave a calendar year with no financial year ending in it, and so with no company tax return for that tax year. If two financial years of an Oy end in one calendar year, each gets its own return and their income is taxed together in that year; a toiminimi puts both on one Form 5.

Tax prepayment. After the change, check the instalments in MyTax and apply for a change if your profit estimate differs; see our article on tax prepayment.

VAT. VAT periods are set by the calendar (Act on the Assessment Procedure for Self-Assessed Taxes, section 11), so VAT returns continue as before.

Worked example: from calendar year to 1 July – 30 June

Example Oy rents out skis. Its busiest months are December to March, and it wants its year to end on 30 June, when the season is over and the stock is back in the store. Its year has been the calendar year, written in its articles. In spring 2027 it has two choices.

In both cases the 2026 tax return is due on Friday 30 April 2027, and the AGM that adopts the 2026 accounts by 30 June 2027 can also decide the change; for option A it must meet in time to notify by the end of April. The PRH fee is 355 euros, because the year is in the articles.

Option A adds a year-end close in 2027, but the accounts follow the season at once. The 2027 tax year is the six-month year alone.

Option B saves a year-end close. No financial year ends in 2027, so there is no company tax return for the 2027 tax year; the next Form 6B covers all 18 months. The catch: if PRH has not registered the change by 31 December 2027, the year ends then, as registered.

Frequently asked questions

How long can a financial year be in Finland?

12 months as the rule. A first year, a last year or a year in which the year end changes can be shorter, or longer up to 18 months.

Can a toiminimi choose a financial year other than the calendar year?

Only if it keeps double-entry books. On single-entry books a sole trader's financial year is always the calendar year.

Can I change the financial year retroactively?

No. For an Oy the change takes effect when PRH registers it, which must happen before the year being changed ends. For a toiminimi it takes effect when the Tax Administration has processed the notice.

Does changing the financial year change the VAT period?

No. VAT periods follow calendar months, quarters or years, whatever your financial year.

When is the tax return due after the change?

For an Oy, four months after the end of the last calendar month of the financial year: for a year ending 30 June, by 31 October, or the next business day if that is a weekend or holiday. A toiminimi files its Form 5 by its usual deadline the following spring. All the year-end dates are in our article on financial statements deadlines, and the steps in year-end closing.

What we do

We keep the books for small limited companies, plan the transitional year with you, prepare the decision and file the change notification once you have authorised us in YTJ. The year-end close and the company tax return then follow the new dates. See limited company accounting or request a quote.

Sources

• Finlex: Accounting Act 1336/1997, chapter 1 section 4 (in Finnish)
• Finlex: Limited Liability Companies Act 624/2006, chapter 5 sections 1, 3 and 27 and chapter 8 sections 4 and 10 (in Finnish)
• Finlex: Act on Assessment Procedure 1558/1995, section 3 (in Finnish)
• Finlex: Act on the Assessment Procedure for Self-Assessed Taxes 768/2016, section 11 (in Finnish)
• Finnish Patent and Registration Office: changing the financial year of a limited company (in Finnish)
• Finnish Patent and Registration Office: fees for changes and closures (in Finnish)
• Tax Administration: changes to the financial year (in Finnish)
• Tax Administration: business tax return of a sole trader, filing instructions (in Finnish)
• YTJ: instructions for change notification Y6, financial year (in Finnish)
• Finnish Patent and Registration Office: mandatory electronic filing (in Finnish)
• Tax Administration: income tax return of a limited company
• Tax Administration: income taxation of limited companies (in Finnish)
• Tax Administration: how often prepayment is paid (in Finnish)
• Tax Administration: decision on companies' prepayment instalments A64/200/2018 (in Finnish)
• Tax Administration: changing the VAT period (in Finnish)

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.

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