Every time you buy or sell an ETF you pay an invisible cost — the bid-ask spread and market impact. Understanding these makes you a sharper ETF trader and can save you real money on large orders.
Explore India's ETF Directory →When you open the order book of any ETF on Zerodha, Groww or Upstox, you see two prices — the bid (best buy offer) and the ask (best sell offer). The difference between them is the bid-ask spread.
If you buy at ₹250.15 and immediately sell, you'd receive only ₹250.05 — a round-trip cost of ₹0.10 per unit (0.04%). This is your immediate mark-to-market loss on the trade. For small retail orders of NIFTYBEES it's tiny. For large orders in a thinly-traded sectoral ETF, it can be significant.
Key rule: A wide bid-ask spread is not a sign that the ETF is "expensive" to own long-term. It's a sign that few market makers are competing to provide liquidity. The remedy is using limit orders — placing your order at or between the bid and ask rather than accepting the market price.
This two-layer structure means that a Nifty 50 ETF with seemingly low daily volume can still handle a ₹10 Cr order efficiently — because an authorised participant (AP) can create new units on demand. An ETF's "true" liquidity is the liquidity of what it holds, not just what trades on screen.
The gap between market price and iNAV (expressed as a %) is called the premium or discount. A well-functioning, liquid ETF should trade within ±0.10% of iNAV for most of the trading day. A large, persistent premium or discount signals poor liquidity or a market-making breakdown.
⚠️ Watch out: International ETFs (e.g., those tracking US or global indices) often show large premiums or discounts during Indian market hours because the underlying US markets are closed. The iNAV is based on stale prices. NSE typically halts creation/redemption for these ETFs during their local market's non-trading hours, so the premium can persist for hours.
Impact cost is the cost of executing a large order beyond the best available price. If the best ask for BANKBEES is ₹52.00 for 5,000 units, but you want 50,000 units, you'll have to work through higher ask prices in the order book. Your average fill price will be above ₹52.00 — that difference is impact cost.
NSE itself uses impact cost (for a ₹10 Cr order) as a key criterion for index eligibility. A stock must have impact cost ≤ 0.50% to be eligible for Nifty 50. This ensures that the stocks inside your ETF are themselves liquid enough for the fund manager to transact without excessive slippage.
For retail investors (buying 10–1,000 units), impact cost is negligible in large-cap ETFs. For institutions or HNIs deploying ₹1 Cr+, it is worth splitting large orders across multiple trading sessions or using a broker's block deal facility.
| ETF Category | Typical Spread | Typical Daily Volume | Best For |
|---|---|---|---|
| Large-Cap (Nifty 50, Sensex) | 0.01–0.05% | ₹100–500 Cr/day | Any order size, any time |
| Banking (Nifty Bank) | 0.02–0.08% | ₹20–100 Cr/day | Good for retail, manageable for institutions |
| Gold ETFs | 0.02–0.06% | ₹10–60 Cr/day | Good liquidity, spread tight throughout day |
| Midcap / Smallcap ETFs | 0.05–0.20% | ₹2–20 Cr/day | Use limit orders, avoid market orders |
| Sectoral / Thematic ETFs | 0.10–0.40% | ₹0.5–10 Cr/day | Patience required; limit orders essential |
| International ETFs | 0.10–1.00%+ | ₹1–15 Cr/day | Large premiums possible; check iNAV first |
| Debt / Liquid ETFs | 0.01–0.05% | ₹5–50 Cr/day | Excellent for parking short-term cash |
Market makers (officially called Authorised Participants or APs in India) are SEBI-registered entities that have a special agreement with the AMC. They continuously post bid and ask quotes for the ETF, profiting from the spread. Their ability to create and redeem ETF units at NAV is what keeps the market price anchored to fair value.
When the ETF price rises above iNAV (premium), an AP can buy the underlying basket of stocks, deliver it to the AMC, receive new ETF units, and sell them on the exchange — pocketing the premium. This arbitrage activity increases the supply of units and drives the price back down toward iNAV.
Conversely, when the price falls below iNAV (discount), an AP buys ETF units on the exchange, redeems them with the AMC for the underlying stocks, and sells those stocks — earning the discount as profit. This removes units from circulation and pushes the price back up.
Bottom line: The creation-redemption mechanism is the backbone of ETF pricing efficiency. It's why large-cap Indian ETFs trade very close to NAV throughout the day — multiple APs are constantly arbitraging any gap. Thinly-traded ETFs with few APs can persistently trade at premiums or discounts of 0.5–2%.