For pension insurance/occupational pension, an annual yield tax is payable. If your pensions are in the process of being paid, they are also taxed for income. You do not need to do anything yourself but instead the insurance company where your pension is invested will report the yield tax paid any any income tax to the Swedish Tax Agency.
The yield tax is a flat-rate tax that is deducted in advance based on the value of the pension capital on 1 January each year.
The tax calculation is made by multiplying the value as of 1 January by the average government borrowing rate of the previous year. This product is called tax base* which is then multiplied by 15%.
For the year 2020 the tax rate will be 0.075% (0.50% * 15%).
*The average government interest rate was 0.03%* in the year 2019 but the tax base must, as of 2017, be at least 0.5% of the pension capital.
A mathematical example:
You have SEK 100,000 in entry value 2020.
Yield tax = SEK 100,000 * 0.50% * 15% = SEK 75.
For income tax we refer to the Swedish Tax Agency's website for information about the regulations and levels applicable at any given time. It is common that the cut-off limit for marginal tax is higher for pensioners as the basic deduction is larger.