With regard to the planned exchange offer of 1.25 Sampo share for 1 Topdanmark share and possible tax consequences of shareholders of Topdanmark that are tax resident in Finland the following applies (source Prospectus page 188). I am writing this as I assume that some of you own Topdanmark shares (according to Nordnet there are ca 6000 Topdanmark shareholders, of I am sure some are from 
Tax Implications of the Exchange Offer
"Under Section 52 f of the Finnish Business Income Tax Act, an exchange of shares is a corporate reorganization in which a limited liability company acquires a holding in the capital of another limited liability company such that it obtains a majority of the voting rights in that company, or, holding such a majority, acquires a further holding, in exchange for the issue to the shareholders of the latter company, in exchange for their securities, of securities representing the capital of the former company. Consideration may also be paid in cash, to the extent the amount does not exceed 10 per cent of the
amount paid in share capital corresponding to the shares given as consideration (or, where the shares have a nominal value, of the nominal value of the shares issued).
Based on a pre-emptive discussion, Sampo has received a binding written confirmation from the Finnish Tax Administration on the tax treatment of the Exchange Offer. It has been confirmed in the written confirmation that provisions of Section 52 f of the Finnish Business Income Tax Act apply to the Exchange Offer, provided that cash proceeds paid to tendering Topdanmark shareholders in lieu of their entitlement to fractional Exchange Offer Shares do not exceed 10 per cent of the amount paid in share capital corresponding to the shares given as consideration. Any redemption price paid to Topdanmark shareholders demanding redemption of their shares should not be deemed as cash consideration within the meaning of Section 52 f of the Finnish Business Income Tax Act.
If the offer consideration is paid in shares in Sampo as the recipient company and the above described criteria under Section 52 f of the Finnish Business Income Tax Act is met, the Exchange Offer is not considered a transfer of the shares from the point of view of Topdanmark’s shareholders and, therefore, such share exchange does not cause any direct income tax implications for the shareholders, whereby the acquisition cost of the shares in Sampo received as offer consideration by the shareholders is derived from the acquisition cost of the shares in Topdanmark"
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A am no lawyer but my non-professional interpretation of this would be that Finnish tax residents would not be subject to any tax payments of this transaction.
Please correct me if I am wrong 
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Also (page 184):
"Following the Secondary Listing of the Sampo A Shares, including the Exchange Offer Shares, in the form of share entitlements of Sampo A Shares, to Nasdaq Copenhagen, shareholders can request to transfer and exchange their Sampo A Shares trading on Nasdaq Copenhagen to Sampo A Shares trading on Nasdaq Helsinki.
Shareholders who wish to transfer and exchange their Sampo Shares trading on Nasdaq Copenhagen to Sampo A Shares trading on Nasdaq Helsinki or vice versa must instruct their own custodian banks to transfer their Sampo A Shares from the omnibus account in Euroclear Finland held by Euronext Securities Copenhagen to their own account with Euroclear Finland or vice versa
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Transferring the shares to Helsinki might be benficial if the dividend is taxed based on Danish procedures (27% direct tax, there is no info on this) and also based on volatility, as I would assume/guess there would be barely any trading in Sampo DKK shares (based on the trading history of the Topdanmark share).