How To Write A Letter To Landlord About Security Deposit . A security deposit demand letter is an official document sent to landlords by their tenants, demanding a refund of money paid at the start of the tenancy as proof of an intent to move in and care for the property as stipulated in their lease agreement. I am writing to dispute this claim on my deposit. 50 Effective Security Deposit Return Letters [MS Word] ᐅ TemplateLab from templatelab.com The security deposit or caution fee is a fee the tenant pays to the landlord at the beginning of a tenancy, which can be used to pay for any damage the tenant causes to the rental property. If the landlord does not refund your security deposit in full after you have given him your forwarding address, he must (within 30 days of your vacating the property. I’m including your entire security deposit along with this letter.