When to register a dispute

Tenancy Deposits

I had a tenant leave my property in May this year. The deposit is lodged with the DPS. As soon as possible after the tenant left we obtained quotes for replacing damaged carpets, decorating etc. We wrote to the tenant (who had admitted that he had caused the damage) with a settlement figure. He took weeks to respond disputing the figures asking us to reduce them. As a goodwill gesture, we did, only for him to claim weeks later that he had not received our email. we re sent it and he still disputed things. We made a final offer (we are loathe to go down the route of dispute resolution as, from past experience,do not believe it to be balanced) we have still not had a reply in 3 weeks to our last email. As we had hoped to reach agreement with the tenant, there was, in our minds, no dispute to register with the DPS. dps literature states that disputes should be registered within 10 days of the end of the tenancy. Can we be held responsible for not registering what we did not, initialy appear to be a dispute, and what would be our best course of action now. many thanks, Mike