SD clawback is covered many many times on AAM - basically where a property purchased as an owner occupied PPR is rented out (other than under the owner occupier rent a room scheme) within the first 5 years then the owner is liable for the difference between the SD paid on the original pruchase (possibly 0%) and what an investor would have paid at the time on the same purchase. Your mortgage provider has nothing to do with this. If you should talk to anybody it's an independent tax advisor. But the relevant information is available on the Revenue.