Registrar and transfer agents (RTAs) that process every mutual-fund purchase, SIP and redemption, and keep shareholder records for companies.
Runs the back office for fund houses - investor accounts, SIP mandates, NAV-based transactions, payouts, KYC and statements - paid mostly as basis points on the assets they service. Also handles company share registries, IPO allotments, insurance repositories and pension (NPS) records.
Two companies service the whole mutual-fund industry: CAMS about two-thirds of assets and KFin the rest. Contracts last years and switching is rare, so they grow almost in step with industry AUM - a quieter way to own the SIP story than an AMC.
Fees are a few basis points of AUM on a telescopic scale (falling as each fund house grows), so revenue grows a little slower than AUM. Non-fund businesses - payments, KYC, insurance and NPS records, international fund admin (KFin) - are the growth add-ons.