The taxes and additional payments into the special fund established for this purpose [1] already cover the prospected costs of dismantling all nuclear power stations and treating/storing the waste (spent fuel as well as materials from dismantled reactors). While the additional "effektskatt" has been abolished in 2018 the payments to SKB continue. The total costs are estimated to end up at 171 billion kr allowing for a safety margin and taking price increases into account. Remaining costs as of 2024 are estimated to be 124 billion kr. The fund currently holds 80 billion kr, the additional 'effektskatt' brought in 38.5 billion kr, securities posted by the companies which run the nuclear power stations stand for another 59 billion kr. Payments into the fund continue, the proceeds of which are invested in state bonds and on the stock market. Even without these continuing payments and investments and disregarding compound interest the costs for dismantling current reactors and treating all waste has been paid already. As it stands the plan is for the remaining reactors to run until ~2045 [2]. Payments into the SKB fund will continue so by the time the last reactor is shut down the costs will have been paid several times over.
[1] https://skb.se/det-har-ar-skb/finansiering/
[2] https://www.karnavfallsradet.se/karnavfall-och-slutforvaring...