What a deposit dispute letter should do
A strong deposit dispute letter narrows the disagreement. It should identify each deduction, state whether you accept or reject it, explain why, and ask for the evidence the landlord relies on.
Do not argue only in general terms. Deposit scheme adjudicators usually decide based on documents: inventories, dated photos, check-out reports, invoices, and correspondence.
Use the scheme, not just email
GOV.UK says tenancy deposit protection schemes offer a free dispute resolution service if landlord and tenant disagree about the deposit. There can be time limits, so contact the scheme as soon as possible if the dispute is not moving.
The letter is useful before a formal dispute because it may resolve the issue and shows that you asked for the right evidence. It is not a substitute for starting the scheme process where a deadline applies.
Fair wear and tear
A deposit is not there to make the property better than it was at the start of the tenancy. Age, ordinary use, and the original condition all matter. Your evidence should show the condition at move-in and move-out so deductions can be judged fairly.