Second-hand sublets require written authorization from the landlord or BRF board. Under the Rent Act (Hyreslagen), rents for subleased Bostadsrätt units are strictly capped to capital cost plus utility expenses.
If a sublandlord charges an illegal surcharge (oskälig hyra), the tenant can seek reimbursement of excess rent for up to two years retroactively through the Regional Rent Tribunal (Hyresnämnden).

