First check whether your deposit is registered with one of the approved tenancy deposit schemes and contact that scheme about any dispute. If it has not been protected, write to your landlord or letting agent and ask for the required information and repayment. In England and Wales, you may be able to apply to the county court; Scotland and Northern Ireland have different procedures, so check the relevant guidance on GOV.UK or your nation’s official housing website. A housing adviser or solicitor can explain your options based on your tenancy and evidence.