How do mortgage deeds work and when are they needed?

Mortgage deeds ("pantbrev") are proof that a property is pledged ("pantsättning") as security for a loan, registered with the Land Registry ("Lantmäteriet") and costing 2% of the amount to issue. When buying a house, existing mortgage deeds ("pantbrev") often come with the property, so you only need new ones for the difference. They remain with the property even when loans are paid off, which makes future borrowing easier. For co-op apartments ("bostadsrätter"), you don't need mortgage deeds ("pantbrev") – instead you pledge ("pantsätter") your apartment to the bank with a pledge fee ("pantsättningsavgift") to the association.