You are in foreclosure once you have been served with the Mortgage Foreclosure Lawsuit.
The documents served on you to begin the lawsuit are a Summons and a Complaint. If you own the house being foreclosed and live there the lawsuit papers should include a Notice of Right to Foreclosure Intervention.
The mortgage company says you are in foreclosure it decides to get an attorney to file a foreclosure lawsuit against you. They will say you are “in foreclosure” before you have been served with the Summons and Complaint that starts the lawsuit.