The average cost method (Swedish: genomsnittsmetoden) calculates the cost basis when selling securities of the same class and type, such as shares or options. The cost basis is the average acquisition cost of all holdings of that type, also known as GAV.
The owner needs to know when and at what price each block was acquired, including shares from new share issues and option exercises. A share ledger with complete history makes this easier. See Skatteverket's guidance for the rules.

Average acquisition cost (GAV) is the average price you have paid for your shares.
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An option gives the holder the right, but not the obligation, to buy or sell an asset at a set price.
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Option exercise means the option holder uses their right to buy or sell the underlying asset.
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Form KU31 is a statement of earnings to Skatteverket on dividends and similar on shares and equity rights.
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