Orders and risk
Slippage
Slippage is the difference between the price you expected for an order and the price at which it was actually filled.
Slippage is the gap between the price you expected and the price you got. You click buy at 100, the fill comes at 100.40, and the 0.40 is slippage. It happens on entries, on exits and most of all on stop-loss orders. It can occasionally work in your favour, but over many trades it is a cost.
It has two causes. One is speed: price moves between your decision and the order reaching the exchange. The other is depth: there is not enough quantity at the best price, so a market order eats into the next levels of the order book. Wide bid-ask spreads make both worse.
In Indian markets, Nifty and Bank Nifty futures are liquid and usually slip little in normal conditions. Far out-of-the-money options, low-volume stock futures and thinly traded crypto option strikes are another matter. Slippage also jumps in the first minutes after 9:15 am, around major announcements, and whenever price gaps through a stop-loss.
The common mistake is ignoring it when judging a method. A back-test or a chart assumes perfect fills at the plotted price. Real fills are worse, and with small intraday targets a few points each way can remove most of what the method makes. Record the planned price and the actual fill for every trade, and you will know your own figure.
Worked example
Stop-loss slippage on a Bank Nifty policy day
Illustrative numbers: you sell Bank Nifty futures at 56,000 with a stop-loss at 56,100, a planned risk of 100 points. The RBI policy announcement comes out and price jumps. Your stop-loss triggers at 56,100 but the market order fills at 56,130. The planned loss was 100 points, the actual loss is 130, and the slippage of 30 points has made the loss 30 per cent larger than planned.
In WizeBuySell
WizeBuySell plots levels on your TradingView chart. It does not place orders, so it neither causes nor prevents slippage. The entry, targets and stop-loss you see are chart prices; on the option strategies they are index or Bitcoin levels, and the option itself has its own bid-ask spread. Your fills depend on your broker, your order type and the liquidity of the strike named on the chart.