The law in plain English
Return deadline
Under Mo. Stat. Section 535.300, the deposit response usually has to be sent within 30 days of the move-out timeline described by the state rule.
Required notice
Missouri generally requires an itemized list of deductions and any remaining deposit within 30 days after the tenancy ends.
This dispute type
Once the Missouri deadline passes, the dispute stops being only about the deductions and becomes a deadline-compliance problem too. A landlord may still argue damage existed, but Mo. Stat. § 535.300 sets the clock for returning the balance and explaining any amount withheld.
Penalty leverage
If the withholding was wrongful or in bad faith, the exposure allowed under the statute is: You can recover up to twice the amount wrongfully withheld