Corporation Tax Online
Use your Katso ID and Password to sign in. You must be a holder of one of the following Katso Roles: Admin or Master User, Parallel Master, or Filer of Income Tax Returns. No login is necessary for the tutorial demo version.
MyTax to replace Corporation Tax Online in November 2017
Corporation Tax Online is available up to 31 October 2017 for users filing income tax returns or changing their bank account numbers. However, if you need to submit a new or changed bank account number, we recommend doing so in MyTax.
As of 1 November 2017, Corporation Tax Online will work in read-only mode. This means that users will be able to browse their previously filed tax returns or download them for future use. Read-only mode will continue until 2 May 2018. No income tax returns can be filed in Corporation Tax Online after 31 October 2017.
- Read more about the changes (in Finnish; in Swedish)
Please also note:
- Tax returns must be submitted on 31 October 2017 at the latest. After this, any tax returns saved as "incomplete" in Corporate Tax Online will no longer be visible.
- Any previously submitted or unfinished tax returns in Corporation Tax Online will not be transferred to MyTax for viewing.
- Corporation Tax Online will work in read-only mode until 2 May 2018. If you have any information saved in Corporation Tax Online that you might need, we recommend that you download it.