Liquidity, spreads and slippage

Live Flow shows the last traded price. When you place an order, you deal with something else: the order book, where buyers' bids and sellers' offers wait. How easily you can trade without moving the price is called liquidity, and ignoring it turns good-looking plans into poor trades.

The spread and the depth

At any moment there is a best bid (the highest price a buyer is waiting to pay) and a best ask or offer (the lowest price a seller is waiting to accept). The gap between them is the spread. A market buy order pays the ask; a market sell order receives the bid. Each round trip pays the spread once.

Depth is how much quantity waits at and near those prices. If your order is bigger than what sits at the best price, the rest fills at the next prices, a little worse each time.

Slippage: where stops get hurt most

Slippage is the difference between the price you planned and the price you got. It is usually small on entries you place calmly, and largest exactly when you least want it:

• Stop-loss market orders trigger when price is moving fast against you. They fill at whatever is available, which can be well past your stop in a sharp move.
• Stop-limit orders protect the price but may not fill at all if price jumps through the limit, leaving you in the trade.
• Gaps: an intraday trade has none overnight, but news can make a stock jump several rupees between two ticks.

Plan for a stop that fills somewhat worse than its level, especially in fast markets.

Futures, options and liquidity

• Stock futures trade in fixed lot sizes set by NSE. Liquidity is usually best in the near-month contract.
• Stock options vary enormously. Strikes near the current price in the nearest expiry are usually the most active; strikes far from the price can have wide spreads and little depth, where a market order can cost a lot.
• Live Flow shows stock prices and volume, not option prices or spreads. Always look at the actual contract's depth and spread in your broker's window.

Time of day

• The first minutes after 09:15: spreads can be wider and prices jumpy while overnight orders are absorbed.
• Midday: volume often thins and moves get choppier.
• The last hour: activity usually picks up again into the close.

Costs and spread shrink reward-to-risk

Say a plan has risk ₹5 and reward ₹10 per share: 1:2 on paper. Now add half a rupee of slippage on entry, and about ₹0.30 per share in total transaction costs (brokerage, STT, exchange fees, GST, stamp duty; the exact amount depends on your broker and the instrument):

	On paper	After slippage and costs
Risk if stopped out	₹5.00	₹5.80
Reward if target hit	₹10.00	₹9.20
Reward-to-risk	1 : 2.0	1 : 1.6

SEBI's study found individuals paid about ₹25,000 crore in transaction costs in each of FY25 and FY26 (lesson 1). Costs are not a detail.