First, ask the landlord in writing for the deposit and request a clear explanation for any proposed deductions, keeping your tenancy agreement, payment records, messages, photographs and receipts. If the issue is not resolved, apply to the Residential Tenancies Board (RTB) online and provide the relevant evidence and contact details. The RTB may offer mediation, where the parties try to reach an agreement, or adjudication, where an adjudicator considers the evidence and issues a decision. A party may generally appeal an adjudication decision to a Tenancy Tribunal within the applicable timeframe. The final outcome depends on the facts and evidence in the individual case.