Security deposit rules vary significantly by state and sometimes by city, covering everything from the maximum you can collect to how long you have to return it. This isn't legal advice and isn't a substitute for checking your local law. It's the pattern of mistakes that show up regardless of jurisdiction.
Mistake one: no documented move-in condition. Covered separately, but it's the root cause of most deposit disputes. Without it, a deduction is your word against theirs.
Mistake two: deducting for normal wear and tear. Worn carpet after three years, faded paint, minor nail holes from hanging pictures — these are generally normal wear, not damage, in most jurisdictions. Charging for them is a common way landlords lose deposit disputes.
Mistake three: missing the return deadline. Most states set a strict deadline, often two to four weeks, to return the deposit or an itemized list of deductions. Miss it and some states require you to return the full deposit regardless of legitimate damage, or pay penalties on top.
Mistake four: not itemizing deductions with actual costs. "Kept for damage" isn't itemization. An actual repair invoice or receipt, tied to a specific documented issue, is what holds up if it's ever disputed.
Mistake five: commingling deposit funds. Some states require deposits to be held in a separate account, sometimes with interest paid to the tenant. Treating deposit money as general operating cash is a common and avoidable mistake.
Look up your specific state's rules before you collect your next deposit. The patterns above are close to universal; the specifics aren't.