I already received an answer.
Nowadays, the prospectus states a 50% withholding tax to Finland. I’d almost dare to say that it was 30% when the account was opened.
I also asked how Fortum differs from Sampo.
I sent more questions there.
I guess I can copypaste this here:
Thank you for your email.
Withholding tax is usually withheld by the paying agent of the paying organisation, but withholding can also take place higher up the custody chain. DEGIRO usually receives the income as a net amount, after the deduction of withholding tax.
The reason why the lower tax treaty is not automatically applied is due to the fact that there can be many parties interposed between the beneficial owner and withholding agent, such as (several) foreign and domestic parties in the custody chain (custodians). The withholding agent then withholds the statutory tax rate and not the lower tax treaty rate.
In cases where a lower tax rate should be applied on the basis of a tax treaty, it is occasionally possible to reclaim part of the withheld tax in the source country. To reclaim excess paid withholding tax, a reclaim request needs to be submitted at the tax authorities in the source country. The complexity of the reclaim process varies per country.
Each country adapted its own reclaim procedure. Usually, these procedures are time-consuming, costly, and require the cooperation of different parties. For this reason, it is seldom profitable to start a reclaim procedure.
For more information and applicable tax rate, please see “withholding tax” on our tax page. The withholding tax for Finnland is 50 %.
Please do not hesitate to get back if you have any other questions.
Here are the withholding taxes: