What can I legally deduct from the security deposit?

Only genuine tenant damage beyond fair wear and tear, plus unpaid rent or utility bills and missing furnishings. Everyday wear - minor scuffs, small nail holes, faded paint - isn't deductible, and you can't demand full repainting unless the contract says so. The market norm is 5% of rent (10% furnished); refund on handover, commonly within 30 days.