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.

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.

What does Corporation Tax Online do?

You can file an income tax return (complete with all enclosures) for the 2016 and 2017 taxable year in Corporation Tax Online. You make your filing by keying in your input.

If necessary, you can come back later to open a new session to add more enclosures or more details to your filing.

Who may use Corporation Tax Online?

People who are authorised to represent a limited liability company, a cooperative society or a non-mutual real estate company may use it.

However, foreign corporate entities or companies carrying out agricultural operations cannot use Corporation Tax Online for tax return filing for the 2017 taxable year.

Because you are expected to key in your input on every line, Corporation Tax Online does not accept a tax return that an accounting software program has generated. To send us such a return, go to


29.03.2017 Corporation Tax Online is now available for tax return filing for 2016 – Forms 4, 6, 6B and 6C with their enclosures. Corporation Tax Online is available for returns for tax year 2017 only if Form 4, Form 6 and Form 6B are filed. Form 6B may only be filed if the company has no agricultural income.

Launch the Demo

Demo (tax year 2016)

Demo (tax year 2017)

Demo lets you try out Corporation Tax Online and experiment with the figures of a dummy corporation. Tax Administration does not receive any input you enter into the Demo.

More information

Legal statement regarding the use of stored taxpayer data.