We are a manufacturing company and had crossed 20 employees 8 months back. After realizing this, we registered for PF. We now have 28 employees. Recently, we received a notice from PF inquiring why we were not registered in PF from the company's incorporation date, which was 12 years ago. Could you please clarify if it was mandatory to register in PF from the incorporation date, and what would be the liability for late registration?