The Financial Services Ombudsman has published a note (here) about what a financial institution needs to show to establish to FOS’s satisfaction that, on the balance of probabilities, it sent a document to a customer’s last known address.
We usually suggest that clients have the person that serves the notice complete a proof of service form and attach it to a copy of the default notice that was sent.
We find that using a proof of service form provides sufficient proof and if Court proceedings follow, we have all the service information on the one document that we need for a proof of service affidavit.