Is it permissible for the landlord to ask the tenant for a sum of money as a security deposit, to be returned in full upon the sound handover of the house, with deductions made for the cost of repairing damages or for overdue rent?

If the homeowner rents out the property for a known rent, and requests a sum of money from the tenant as a pledge (security deposit) to guarantee rights, there is no objection to that. This is considered an independent lease and a seized pledge that is returned to its owner. The homeowner must not invest this pledge or benefit from it. However, if the investment of this sum is part of the rent, then this is impermissible due to the uncertainty (Jahalah) and gharar (ambiguity) involved, and it is considered a loan that draws benefit, which is a form of Riba (usury). As for the tenant guaranteeing the leased property, he does not guarantee it except in cases of transgression or negligence.