A folio number is the unique identification number assigned to an investor by a mutual fund house or its Registrar and Transfer Agent (RTA) when they first invest in a scheme. It functions like an account number for that investor within that particular fund house, consolidating all investments made in different schemes of the same AMC under one folio. Investors can have multiple folios across different fund houses. The folio number is essential for tracking transactions, making subsequent purchases or redemptions, updating KYC details, and accessing account statements. Through India's consolidated account statement (CAS) system, all folios and demat holdings linked to a single PAN are aggregated into one unified view.