Secondary Markets: How Stock Trading Works

After a company issues securities through a primary market process such as an IPO, the next interview question is what happens when investors want to trade those already-issued securities. Secondary markets answer that question by turning issued securities into tradable assets through exchanges, order books, safeguards, and settlement. In interviews, this matters because it connects capital markets to liquidity, price discovery, and risk transfer.

How Secondary Markets Create Liquidity and Prices

Secondary markets sit after issuance: securities have already been issued, and investors trade them with each other. The big picture is simple - exchanges provide the venue, the order book matches buy-sell orders, safeguards manage extreme moves, and T+1 settlement completes equity trades the next business day.

India has two major exchanges, NSE and BSE, and both support the infrastructure through which already-issued securities become liquid and continuously priced assets.

NSE vs BSE Comparison

NSE (National Stock Exchange) and BSE (Bombay Stock Exchange) are the two major exchanges in India. The comparison below captures their founding, listed market cap, benchmark indices, derivatives position, settlement, technology, and primary usage.

Why Secondary Markets Matter

The core functions of secondary markets are liquidity, price discovery, and risk transfer. In interview terms, those three points explain why an issued security does not remain static after an IPO or listing event.

• Liquidity - trading of already-issued securities between investors.
• Price discovery - trading activity helps securities reflect market-cleared prices.
• Risk transfer - investors can transfer exposure by buying or selling securities in the market.

Market Microstructure

Market microstructure explains how trading works inside the exchange environment. It includes the order book, circuit breakers, stock price bands, short selling, market makers, and T+1 settlement.

How Trading Works Through the Order Book

The order book is a Central limit order book (CLOB) matching buy-sell orders by price-time priority. In the Indian context, NSE NEAT has ~50,000+ orders/second capacity, and co-location is allowed for HFT.

This is the core mechanism that converts investor buy and sell interest into executed trades. For interviews, the important phrase is price-time priority because it shows how order matching is governed inside the exchange system.

Safeguards and Trading Controls

Secondary markets are not only about matching trades; they also include safeguards that manage volatility and execution risk. Market-wide circuit breakers halt the market when Nifty/Sensex falls 10%, 15%, or 20% intraday.

Individual stock daily limits are typically ±20%, with ±5% or ±10% for volatile stocks. SEBI (Securities and Exchange Board of India) allows exchanges to relax bands on expiry days for derivative-linked stocks.

Short Selling, Market Makers, and Liquidity

Short selling means selling borrowed shares. It has been allowed in India since 2007, covering intraday margin and delivery-based activity.

SEBI restricts naked short selling, with physical settlement for F&O as a 2018 reform. SEBI also mandates market makers for SME IPO stocks and illiquid derivatives, ensuring liquidity in small-cap stocks through an obligation to provide 2-way quotes.

T+1 Settlement

T+1 Settlement means equities are settled next business day from Jan 2023. This reduces counterparty risk.

India was the first major market to adopt T+1, ahead of US, which was still T+2, and EU, which was T+2.

Structuring a Secondary Markets Interview Answer