Does the bid price of a stock change depending on which brokerage I am using?
They could have different quotes as there are more than a few pieces here.  Are you talking a Real Time Level II quote or just a delayed quote?  Delayed quotes could vary as different companies would be using different time points in their data.  You aren't specifying exactly what kind of quote from which system are you using here. The key to this question is how much of a pinpoint answer do you want and how prepared are you to pay for that kind of access to the automated trades happening?  Remember that there could well be more than a few trades happening each millisecond and thus latency is something to be very careful here, regardless of the exchange as long as we are talking about first-world stock exchanges where there are various automated systems being used for trading. Different market makers is just a possible piece of the equation here.  One could have the same market maker but if the timings are different,e.g. if one quote is at 2:30:30 and the other is at 2:30:29 there could be a difference given all the trades processed within that second, thus the question is how well can you get that split second total view of bids and asks for a stock.  You want to get all the outstanding orders which could be a non-trivial task.
In the world of stock exchanges, the result depends on the market state of the traded stock. There are two possibilities, (a) a trade occurs or (b) no trade occurs. During the so-called auction phase, bid and ask prices may overlap, actually they usually do. During an open market, when bid and ask match, trades occur. As others have stated, the current price is simply the last price at which the security traded. For any given tick, however, there are many bid-ask prices because securities can trade on multiple exchanges and between many agents on a single exchange. This is true for both types of exchanges that Chris mentioned in his answer. Chris' answer is pretty thorough in explaining how the two types of exchanges work, so I'll just add some minor details. In exchanges like NASDAQ, there are multiple market makers for most relatively liquid securities, which theoretically introduces competition between them and therefore lowers the bid-ask spreads that traders face. Although this results in the market makers earning less compensation for their risk, they hope to make up the difference by making the market for highly liquid securities. This could also result in your order filling, in pieces, at several different prices if your brokerage firm fills it through multiple market makers. Of course, if you place your order on an exchange where an electronic system fills it (the other type of exchange that Chris mentioned), this could happen anyway.  In short, if you place a market order for 1000 shares, it could be filled at several different prices, depending on volume, multiple bid-ask prices, etc. If you place a sizable order, your broker may fill it in pieces regardless to prevent you from moving the market. This is rarely a problem for small-time investors trading securities with high volumes, but for investors with higher capital like institutional investors, mutual funds, etc. who place large orders relative to the average volume, this could conceivably be a burden, both in the price difference across time as the order is placed and the increased bookkeeping it demands.  This is tangentially related, so I'll add it anyway. In cases like the one described above, all-or-none (AON) orders are one solution; these are orders that instruct the broker to only execute the order if it can be filled in a single transaction. Most brokers offer these, but there are some caveats that apply to them specifically. (I haven't been able to find some of this information, so some of this is from memory).  All-or-none orders are only an option if the order is for more than a certain numbers of shares. I think the minimum size is 300 or 400 shares.  Your order won't be placed until your broker places all other orders ahead of it that don't have special conditions attached to them.  I believe all-or-none orders are day orders, which means that if there wasn't enough supply to fill the order during the day, the order is cancelled at market close.  AON orders only apply to limit orders. If you want to replicate the behavior of a market order with AON characteristics, you can try setting a limit buy/sell order a few cents above/below the current market price. "Assuming that no one else has hit the ask, and the asks are still there, yes, you will fill $54.55 as long as you didn't exhaust that ask. Actually, there is no ""current price at which the stock is exchanging hands""; in reality, it is ""the last price traded"". The somebody who negotiated prices between buyers & sellers is the exchange through their handling of bids & asks.  The real negotiation comes between bids & asks, and if they meet or cross, a trade occurs. It's not that both bid & ask should be $54.55, it's that they were. To answer the title, the reasons why the bid and ask (even their midpoint) move away from the last price are largely unknown, but at least for the market makers, if their sell inventory is going away (people are buying heavily and they're running out of inventory) they will start to hike up their asks a lot and their bids a little because market makers try to stay market neutral, having no opinion on whether an asset will rise or fall, so with stocks, that means having a balanced inventory of longs & shorts.  They want to (sometimes have to depending on the exchange) accommodate the buying pressure, but they don't want to lose money, so they simply raise the ask and then raise the bid as people hit their asks since their average cost basis has risen. In fact (yahoo finance is great about showing this), there's rarely 1 bid and 1 ask.  Take a look at BAC's limit book: http://finance.yahoo.com/q/ecn?s=BAC+Order+Book You can see that there are many bids and many asks.  If one ask is exhausted, the next in line is now the highest.  The market maker who just sold at X will certainly step over the highest bid to bid at X*0.9 to get an 11% return on investment." "This is an old post I feel requires some more love for completeness.  Though several responses have mentioned the inherent risks that currency speculation, leverage, and frequent trading of stocks or currencies bring about, more information, and possibly a combination of answers, is necessary to fully answer this question. My answer should probably not be the answer, just some additional information to help aid your (and others') decision(s). Firstly, as a retail investor, don't trade forex. Period. Major currency pairs arguably make up the most efficient market in the world, and as a layman, that puts you at a severe disadvantage. You mentioned you were a student—since you have something else to do other than trade currencies, implicitly you cannot spend all of your time researching, monitoring, and investigating the various (infinite) drivers of currency return. Since major financial institutions such as banks, broker-dealers, hedge-funds, brokerages, inter-dealer-brokers, mutual funds, ETF companies, etc..., do have highly intelligent people researching, monitoring, and investigating the various drivers of currency return at all times, you're unlikely to win against the opposing trader. Not impossible to win, just improbable; over time, that probability will rob you clean. Secondly, investing in individual businesses can be a worthwhile endeavor and, especially as a young student, one that could pay dividends (pun intended!) for a very long time. That being said, what I mentioned above also holds true for many large-capitalization equities—there are thousands, maybe millions, of very intelligent people who do nothing other than research a few individual stocks and are often paid quite handsomely to do so. As with forex, you will often be at a severe informational disadvantage when trading. So, view any purchase of a stock as a very long-term commitment—at least five years. And if you're going to invest in a stock, you must review the company's financial history—that means poring through 10-K/Q for several years (I typically examine a minimum ten years of financial statements) and reading the notes to the financial statements. Read the yearly MD&A (quarterly is usually too volatile to be useful for long term investors) – management discussion and analysis – but remember, management pays themselves with your money. I assure you: management will always place a cherry on top, even if that cherry does not exist. If you are a shareholder, any expense the company pays is partially an expense of yours—never forget that no matter how small a position, you have partial ownership of the business in which you're invested. Thirdly, I need to address the stark contrast and often (but not always!) deep conflict between the concepts of investment and speculation. According to Seth Klarman, written on page 21 in his famous Margin of Safety, ""both investments and speculations can be bought and sold. Both typically fluctuate in price and can thus appear to generate investment returns. But there is one critical difference: investments throw off cash flow for the benefit of the owners; speculations do not. The return to the owners of speculations depends exclusively on the vagaries of the resale market."" This seems simple and it is; but do not underestimate the profound distinction Mr. Klarman makes here. (and ask yourself—will forex pay you cash flows while you have a position on?) A simple litmus test prior to purchasing a stock might help to differentiate between investment and speculation: at what price are you willing to sell, and why? I typically require the answer to be at least 50% higher than the current salable price (so that I have a margin of safety) and that I will never sell unless there is a material operating change, accounting fraud, or more generally, regime change within the industry in which my company operates. Furthermore, I then research what types of operating changes will alter my opinion and how severe they need to be prior to a liquidation. I then write this in a journal to keep myself honest. This is the personal aspect to investing, the kind of thing you learn only by doing yourself—and it takes a lifetime to master. You can try various methodologies (there are tons of books) but overall just be cautious. Money lost does not return on its own. I've just scratched the surface of a 200,000 page investing book you need to read if you'd like to do this professionally or as a hobbyist. If this seems like too much or you want to wait until you've more time to research, consider index investing strategies (I won't delve into these here).  And because I'm an investment professional: please do not interpret anything you've read here as personal advice or as a solicitation to buy or sell any securities or types of securities, whatsoever. This has been provided for general informational purposes only. Contact a financial advisor to review your personal circumstances such as time horizon, risk tolerance, liquidity needs, and asset allocation strategies. Again, nothing written herein should be construed as individual advice." I think your confusion has arisen because in every transaction there is a buyer and a seller, so the market maker buys you're selling, and when you're buying the market maker is selling. Meaning they do in fact buy at the ask price and sell at the bid price (as the quote said). You bought 1 share of Google at $67.05 while it has a current trading price of $1204.11. Now, if you bought a widget for under $70 and it currently sells for over $1200 that is quite the increase, no? Be careful of what prices you enter into a portfolio tool as some people may be able to use options to have a strike price different than the current trading price by a sizable difference. Take the gain of $1122.06 on an initial cost of $82.05 for seeing where the 1367% is coming. User error on the portfolio will lead to misleading statistics I think as you meant to put in something else, right? Mutual funds don't work like stocks in that way. The price of a mutual fund is set at the end of each day and doesn't fluctuate during the day. So no matter when you put in your order, it will be filled at the end of the day at whatever the closing price is for that day. Here is some good information on that There is no continuous pricing of fund shares throughout the trading   day. When an investor places an order to buy or sell a fund's shares,   the order is executed based on the NAV calculated at the end of that   trading day, regardless of what time during the day the order was   placed. On the other hand, if the investor were to check the price of   his or her fund shares halfway through the business day, the price   quoted would be the previous day's NAV because that was the last time   the fund calculated and reported the value. -http://www.finweb.com/investing/how-mutual-funds-are-priced.html They can sell a lower price call if they expect the stock to plummet in the near term but they are bullish on the longer term. What they are looking to do is collect the call premium and hope it expires worthless.  And then again 'hope' that the stock will ultimately turn around. So yes, a lot of hoping.  But can you explain what you mean by 'my brokerage gives premiums for prices lower than the current price'? Do you mean you pay less in commissions for ITM calls?