Proof of payment is on the landlord.
A landlord who says the deposit was refunded must prove the tenant received it.
A tenant disputed ever receiving the refund cheque, and the first court still treated the landlord as released. The Cour de cassation set that aside: whoever claims to have paid must prove it, and the 10% monthly late penalty applies until the deposit is really back.
Lesson: ask for a traceable refund (bank transfer or registered letter), keep every proof, and claim the 10% penalty if the deposit is late.
The decision explained Case reference: Cass. 3e civ., 12 février 2026, n° 24-21.258