When you log in to MyTax, your tax-related letters will change from paper to electronic form automatically. Read more about the changes.
Business taxpayers and corporate entities can use this form to claim a combined deduction based on research and development costs (under the act on additional deductions based on R&D expenses (Laki tutkimus- ja kehittämistoiminnan menoihin perustuvista lisävähennyksistä verotuksessa 1298/2022))
If you want to claim a temporary deduction based on sub-contracting invoices related to research cooperation, use Form 67A.
Submit the information in MyTax as part of the tax return.
Need instructions for filling in the fields? If so, you can read the instructions for completing the paper form.
You can also give the information electronically by uploading a file in the Ilmoitin.fi service.
If you use Ilmoitin.fi, send us the attachment forms together with the main tax return form.
Do not send any paper forms if you use an online channel for filing the company’s tax return.
Guidance for income tax returns as software files — specifications of data formats
Limited liability companies and other corporations filing on paper must send the tax return and its enclosures to the address:
Finnish Tax Administration
OCR Service of corporate taxpayers’ returns
P.O. Box 200
FI-00052 VERO
Self-employed operators of a trade or business, general and limited partnerships as well as agricultural operators and partnerships must send the paper form enclosed with the tax return.
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The online authorisation mandate
You can use the Suomi.fi Authorization to enable you to deal with taxes for another person – including legal persons, companies, other entities – through e-services, over the telephone, or by visiting a service point on their behalf.
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Letters of authorisation on paper
You can receive a letter of authorisation written in the name of a company, to manage a single tax-related issue. If you – either personally or for an organisation that had been authorised – submit tax-related information on paper, a copy of the letter of authorisation has to be enclosed. A letter of authorisation does not provide access to MyTax.
Power of attorney for managing the taxes of a company (3804)
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Page last updated 3/12/2026