When you buy shares in a housing company and thereby gain possession of an apartment in a high-rise building or townhouse, you must pay transfer tax and file the return to report it. Buyers are required to calculate the amount and make the payment by themselves. Exemptions from transfer tax may apply if you are a first-time homebuyer.
At the moment (2019) the transfer tax is 2% of the price of an apartment, including any unpaid part of any housing-company loan.
When you purchased a newly constructed house or apartment, the paiment shall be made and return filed in 2 months after the date of transfer of ownership
The housing company management organisation shall be informed on the transfer tax payment completion in order to have the new shareholder name entered in the list of shareholders.
Please see Finnish Tax Office net pages (link below) for futher information on Transfer Tax