Imagine that a stock costs 100$, you set a limit buy order at $105. Wouldn't this cause the bid/ask spread to jump upwards? Of course this order would get filled immediately, but shouldn't it get filled quite a bit above $100? Thus altering the 'last' price of a stock?

Or would your limit order just get filled by the lowest ask and nothing would particularly change?

  • While not a direct answer to your detailed question, the answer to your subject is definitely (not using limit orders though). If you pick a stock with very little volume, it’s easy to move the price - I did that myself a decade ago and I had to wait many months before the price hit break even. Commented May 5, 2020 at 1:00

1 Answer 1


In the USA, National Best Bid and Offer (NBBO) is the SEC rule that requires brokers to guarantee that customers receive the best ask price when they buy securities and the best bid price when they sell securities. Therefore, your order would get filled at the lowest ask price which is $100, assuming that $100 is the ask price.

Only orders with price improvement cause the B/A spread to change. Those that do not just go on the order book behind those who are offering better prices. For example, the B/A is $100.00 x $100.50. A buy order at $100.05 or a sell order at $100.45 would affect (narrow) the spread.

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