Accounting firm or other agent: how to request authorisation to take care of someone else’s tax matters

If you need authorisation to take care of another person’s, a company’s or an organisation’s tax matters electronically, you can request an authorisation on

Note that the authorising party must accept your request. The method of acceptance depends on whether the authorising party has personal e-bank codes, a mobile certificate or a certificate card.

How to request authorisation


Find out which authorisations you need

The “Managing of tax affairs” authorisation allows you take care of all the authorising party’s tax matters. The other authorisations allow you to take care of only some specified matters.

Read the descriptions of different authorisations to decide which authorisation you need

You can select the authorisation later in the e-authorisation service.


Request an authorisation on

Log in to the e-authorisation service with your personal e-bank codes, a mobile certificate or a certificate card. After that, you can submit an authorisation request to take care of your client’s matters.

Go to the e-authorisation service

Instructions on Request a mandate as a company or an organisation


Ask the client to accept your authorisation request

A) If the client has personal e-bank codes, a mobile certificate or a certificate card, ask them to log in to the e-authorisation service and accept your authorisation request. 

The authorisation request must be accepted separately by each party if the Articles of Association state that the right to sign for the company rests with:

  • the members of the Board all together (limited company, housing company, foundation, association) 
  • two members of the Board together (limited company, housing company)
  • the chairman of the Board together with a Board member (limited company, housing company). e-authorisation service

Instructions on Grant a mandate as a company or an organisation

Instructions on Grant a mandate for transactions as a person

B) If the client does not have an identification token, ask them to go to a tax office and take a passport, photo ID card, driving licence or some other identification with a photo with them. The person must be identifiable from the photo. The client can accept the authorisation request at the tax office, but they must go there in person.

If one person goes to the tax office to accept the authorisation request on behalf of all parties, they will also need to have

  • a power of attorney showing that they have the right to sign on behalf of all the parties (the power of attorney may not be more than 6 months old)
  • photocopies of the passports or photo ID cards of all the parties who are not present at the tax office
  • a copy of the list of parties to the estate included in the deed of estate if the estate has a Business ID.

Contact details for tax offices


You can take care of the authorising party's tax matters electronically

When your request for an authorisation has been accepted, you can log in to the Tax Administration’s e-services with your personal e-bank codes, a mobile certificate or a certificate card. 

After logging in to MyTax, select “Act on behalf of a company” or “Act on behalf of someone else”, depending on whether you are taking care of a company’s or an individual’s tax matters.

An accounting firm may grant an accountant access to only certain customers’ data

The accounting firm can decide which customers’ data each accountant can see in MyTax. When the accounting firm authorises its employees to manage customers’ matters, it can use specifiers to assign certain customers to a certain accountant. Thanks to specifiers, such as customer IDs, the accountants can see in MyTax the details of only those customers whose matters they manage.

Frequently asked questions

If you are a private guardian, you cannot use MyTax or the Tax Administration’s other e-services on behalf of the individual under your guardianship unless they can use electronic identification and grant you the authorisation to do so. In this case, you can fill out tax forms on paper and submit them on the other person’s behalf.

Go to for more information on when you can and cannot act on behalf of someone else

Starting 1 July 2021, if you use a strong personal identifier to log in, your authorisation is no longer checked in the list of Katso service authorisations. You need a authorisation to replace the Katso authorisation.

You can use the service with your Katso ID until your authorisation is in place. Please note, however, that the Katso identification system is discontinued on 31 August 2021.

When you identify yourself to the service with your online banking codes, a mobile certificate or a certificate card, your authorisation to handle matters on behalf of the organisation will be checked with the

  • Trade Register
  • Business Information System (BIS)
  • Register of Associations
  • Authorisations service.

Instructions on how to unlock a locked Katso ID (PDF)