Flagging (Swedish: flaggning or uppflaggning), also known as major shareholding notification, means that anyone trading shares in a listed company must notify it when the holding crosses certain thresholds of shares or votes. Notice goes to the company and Finansinspektionen and is made public, so the market knows who is building a larger block of shares.
The rules apply to listed companies. In companies with unlisted shares, it is instead the share ledger that shows the ownership and how it changes.

A listed company is a public limited company whose shares are admitted to trading on a regulated market.
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A block of shares is a consecutive series of share numbers held by the same owner with the same history.
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A corner is a block of shares large enough to prevent compulsory redemption of the other shares.
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A majority shareholding means one or more owners together hold more than half of the shares or votes.
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