@nemobis You can always do an oikaisuvaatimus (even to request to pay more tax) and wait a couple of years. I’ve done that, and in the end I was told in great detail with reference to the relevant laws that no, I didn’t need to pay more.
(This related to a period when I was domiciled in Finland and working mostly in the UK but also in Finland; my UK tax was refunded when I ceased to work there as it was below the tax threshold. I applied to pay it in Finland anyway, but was told that I was not eligible to pay more tax as the UK income had been from a public sector employer.)