The stock shows ₹100 on your screen. You place a buy order for 100 shares, then open the trade record. Your average purchase price is ₹100.38.
Why didn't you get ₹100?
Before assuming something went wrong, check which number you were looking at. LTP means last traded price. It tells you where the latest trade happened. It doesn't promise that someone is still willing to sell all 100 shares to you at that price.
Let's build a small, made-up order book and follow your purchase through it. By the end, you'll be able to account for the extra ₹38 and see what a different order instruction would have changed.
What was available when you clicked Buy?
The bid tells you what a buyer is currently offering for a stated quantity. The ask tells you what a seller is currently requesting for a stated quantity. LTP tells you about a trade that already happened.
The difference between the best bid and ask is the spread. If the highest bid is ₹99.80 and the lowest ask is ₹100.20, the quoted spread is ₹0.40 per share. Neostox's stock-order guide explains the order choices you’ll encounter when deciding which price to accept.
The last transaction might still be displayed at ₹100. Neither current offer has to equal it. Orders can be added, cancelled or matched after that transaction. A quiet instrument may retain an old LTP even while its available quotes change.
Follow your 100-share order
Imagine the screen displays an LTP of ₹100. The best ask is ₹100.20 for 40 shares, and another seller offers 60 shares at ₹100.50. You submit a market order to buy 100 shares.
If nobody else takes those offers and the sellers leave them in place, the order could buy 40 shares at ₹100.20 and 60 at ₹100.50. The total cost is ₹4,008 + ₹6,030 = ₹10,038 before charges.
The average fill is ₹100.38 per share. Your order has not necessarily malfunctioned because it filled above the ₹100 LTP. It has used the available selling offers. Other buyers can get there first, and sellers can change their offers. That’s why the real fill may differ from this snapshot.
A last-traded price isn’t a guaranteed market-order price. You can explore the difference with virtual money on Neostox's paper trading platform, while checking how the simulator handles fills. For real orders, confirm the applicable exchange and broker rules rather than assuming simulated execution will match them.
Now use a simpler example with a bid of ₹99.80 and an ask of ₹100.20. Suppose you buy ten shares at ₹100.20 and immediately sell all ten at ₹99.80, with quotes unchanged and enough quantity available on both sides.
You pay ₹1,002 and receive ₹998. The ₹4 difference is a gross trading loss from buying at the ask and selling at the bid. Any applicable charges would make the net result worse.
There is no need for the wider market to make a large move for this to happen. The spread already separates the two prices. A display that marks your open position using LTP may show a different temporary figure from the amount you could actually receive by selling.
A best ask of ₹100.20 for 40 shares isn’t an offer to sell unlimited shares at ₹100.20. The available quantity is part of the quote. A larger order may use several price levels or remain partly unfilled, depending on the order instructions.
Don’t estimate a large purchase by multiplying the best ask by every share you want. First look at the quantities available across the relevant levels. Those visible quantities are also only a snapshot, because other participants can act before your order arrives.
Neostox's explanation of liquidity and market depth gives the broader context. Here, the practical question is narrower: how much quantity could be matched near the price you’re using for your calculation?
Would a limit order have changed this?
Use the weighted fill price when reconciling a completed order. Adding the individual fill prices and dividing by the number of executions is wrong if execution quantities differ. For the earlier example, 40 shares at one price and 60 at another must contribute in proportion to their quantities.
A buy limit order sets the highest price you’re willing to pay. If you set a ₹100 limit while the lowest ask is ₹100.20, the order may wait rather than execute. You have controlled the acceptable price, but you’ve not ensured that a seller will trade with you.
Even when the market trades at your limit, your entire quantity may not fill. Other orders can be ahead of yours, and the available quantity may be insufficient. Seeing that price on a chart doesn’t prove your whole order would have filled there.
A sell limit works in the opposite direction: it sets the minimum acceptable sale price. Always check that you selected the correct order side before interpreting the limit.
The same check matters with options
For an option, a small-looking absolute spread can be large relative to the premium. A ₹1 spread on a ₹10 premium is 10% of that reference price; the same ₹1 on a ₹100 premium is 1%. These are simple comparisons, not acceptable-spread thresholds.
Now multiply that price difference by the number of units you’re trading. Keep premium per unit separate from the total amount for all units in your position. Don’t borrow a lot size from another instrument or expiry when checking the total.
The Neostox options-chain tools provide a place to study contract information during virtual practice. Its website currently states that market prices are delayed by 30 days. Compare observations from the same simulated time rather than combining them with a current live quote elsewhere.
Keep the fill record open
Write down the instrument, timestamp, order side, order type, quantity, LTP, visible bid and ask, and actual fill. For a split fill, keep the individual prices and quantities before calculating the weighted average.
Then identify which comparison you’re making. A fill against LTP, a fill against the earlier best ask and a fill against an intended limit are three different checks. Naming the reference prevents a vague claim that the price was wrong.
That ₹100.38 purchase now has an explanation. Forty shares cost ₹100.20 each and sixty cost ₹100.50 each. You spent ₹10,038 before charges. The ₹100 LTP wasn't an offer for your whole order.
Next time a fill surprises you, keep the trade record open and check the quantity at each price. “The screen said ₹100” is the beginning of the question. The individual fills tell you what actually happened to your order.