Impact Cost

A friend showed me his trading app last week, genuinely pleased that it charges zero brokerage. Then he forwarded the fill prices on a small cap he had bought and sold the same week. He had paid a real fee on that round trip. It was nowhere on the contract note, because it was never going to be.

The fee is the spread. Every stock has two prices at once, the price you can buy at and the lower price you can sell at, and the gap between them is yours to pay. You buy at the ask, you sell at the bid, and that gap is gone before the stock has moved a rupee in either direction. Nobody charges it to you. You simply receive a slightly worse price than the one glowing on the screen.

On a liquid Nifty 50 name the gap is tiny, often a tenth of a percent for a full round trip. On a thinly traded small cap it can run to four percent. Same Rs 100000 ticket, in and out: roughly Rs 100 on the liquid stock, roughly Rs 4000 on the thin one. Both apps show the identical brokerage. Zero. The cost that actually mattered, twenty times larger on one than the other, was sitting in the price the whole time.

Here is the part that stays with me. The exchange takes this fee more seriously than most of us do. A stock has to trade at an impact cost of 0.50 percent or less to even make it into the Nifty 50. NSE measures it, publishes it, and uses it as an entrance exam. Your statement still will not say a word about it.

The good news is the cost scales with two things you control. How thin the stock is, and how often you trade it. Liquid names, sized positions, and a rule that moves the portfolio instead of a hand that itches to. Every round trip you do not take is a fee you simply keep.

Zero brokerage was never zero cost. The fee just moved off the receipt and into the price