HDB Financial Services, a subsidiary of HDFC Bank, has filed preliminary papers with Sebi for a Rs 12,500 crore IPO.The IPO will consist of a fresh issue of equity shares worth Rs 2,500 crore and an Offer-for-Sale (OFS) of Rs 10,000 crore by HDFC Bank.The proceeds from the IPO will be used to strengthen the Tier-I capital base and support future lending for business growth.HDB Financial Services will continue as a subsidiary of HDFC Bank after the IPO.