When you log in to MyTax, your tax-related letters will change from paper to electronic form automatically. Read more about the changes.
Have you bought construction services? You can be the constructor, a contractor, a subcontractor or other contractor in the construction project.
As the buyer of construction services, you must file a report on the contracts you have bought to the Tax Administration.
Choose your filing method
If you are filing large amounts of data in one batch, use Ilmoitin.fi.
Instructions for reporting – data format specification for contract details (VSURAKKA)
If you cannot file online, you can use the paper form. You can find the return address on the first page of the form. If you are filing details on multiple contracts, also file Form 3723e.
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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 6/16/2026