Sell a stock and buy a new one
You have to wait for three (business) days. That's the time it takes for the settlement to complete and for the money to get to your account. If you don't wait - brokers will still allow you to buy a new stock, but may limit your ability to sell it until the previous sale is settled. Here's a FAQ from Schwab on the issue. It depends on the broker. The one I use (Fidelity) will allow me to buy then sell or sell then buy within 3 days even though the cash isn't settled from the first transaction. But they won't let me buy then sell then buy again with unsettled cash. Of course not waiting for cash to settle makes you vulnerable to a good faith violation.
At any given time there are buy orders and there are sell orders.  Typically there is a little bit of space between the lowest sell order and the highest buy order, this is known as the bid/ask spread.  As an example say person A will sell for $10.10 but person B will only buy at $10.00.  If you have a billion shares outstanding just the space between the bid and ask prices represents $100,000,000 of market cap. Now imagine that the CEO is in the news related to some embezzlement investigation.  A number of buyers cancel their orders.  Now the highest buy order is $7.  There isn't money involved, that's just the highest offer to buy at the time; but that's a drop from $10 to $7.  That's a change in market cap of $3,000,000,000.  Some seller thinks the stock will continue to fall, and some buyer thinks the stock has reached a fair enterprise value at $7 billion ($7 per share).  Whether or not the seller lost money depends on where the seller bought the stock.  Maybe they bought when it was an IPO for $1.  Even at $7 they made $6 per share. Value is changing, not money.  Though it would be fun, there's no money bonfire at the NYSE. Have the reasons you originally purchased the stock changed? Is the company still sound? Does the company have a new competitor? Has the company changed the way they operate? If the company is the same, except for stock price, why would you change your mind on the company now? ESPECIALLY if the company has not changed, -- but only other people's PERCEPTION of the company, then your original reasons for buying it are still valid.  In fact, if you are not a day-trader, then this COMPANY JUST WENT ON SALE and you should buy more. If you are a day trader, then you do care about the herd's perception of value (not true value) and you should sell. DAY TRADER = SELL BUY AND HOLD (WITH INTELLIGENT RESEARCH) = BUY MORE "The penny/pink sheet stocks you tend to see promoted are the ones a) with small public floats or, b) they are thinly traded.  This means that any appreciable change in buy/sell volume will have an outsized effect on the stock's share price, even when the underlying fundamentals are not so great.  Promoters are frequently paid based on how much they can move a stock's price, but such moves are not long-lasting.  They peter out when the trading volumes return to more normal ranges for the stock because all of the hype has died out. There are some small-cap NASDAQ stocks which can be susceptible to promotion for the same reason -- they have small floats and/or are thinly traded.  Once someone figures out the best targets, they'll accumulate a position and then start posting all kinds of ""news"" on the web in an effort to drum up interest so they can sell off their position into the buying that follows.   The biggest problem with penny/pink sheet stocks is that they frequently fail to publish reliable financial statements, and their ownership is of a dubious nature.  In the past, these types of stocks have been targeted by organized crime syndicates, which ran their own ""pump and dump"" operations as a way to make relatively easy money.  This may still be true to some extent today.   Be wary of investing in any publicly-traded firm that has to use promoters to drum up investor interest, because it can be a serious red flag.  Even if it means missing out on a short-term opportunity, research the company before investing.  Read its financials, understand how it has behaved through its trading history, learn about the products/services it is selling.  Do your homework.  Otherwise you are doing the investing equivalent of taking your money and lighting it on fire. Remember, there's a good reason these companies are trading as penny/pink sheet stocks, and it generally has nothing to do with the notion (the promoters will tell you) that somehow the ""market has missed out on this amazing opportunity.""  Pump and dump schemes, which lie at the heart of almost all stock promotion, rely on convincing you, the investor, that you're smart enough to see what others haven't.  I hope this helps. Good luck!" "It's impossibly difficult to time the market. Generally speaking, you should buy low and sell high. Picking 25% as an arbitrary ceiling on your gains seems incorrect to me because sometimes you'll want to hold a stock for longer or sell it sooner, and those decisions should be based on your research (or if you need the money), not an arbitrary number. To answer your questions: If the reasons you still bought a stock in the first place are still valid, then you should hold and/or buy more. If something has changed and you can't find a reason to buy more, then consider selling. Keep in mind you'll pay capital gains taxes on anything you sell that is not in a tax-deferred (e.g. retirement) account. No, it does not make sense to do a wash sale where you sell and buy the same stock. Capital gains taxes are one reason. I'm not sure why you would ever want to do this -- what reasons were you considering? You can always sell just some of the shares. See above (and link) regarding wash sales. Buying more of a stock you already own is called ""dollar cost averaging"". It's an effective method when the reasons are right. DCA minimizes variance due to buying or selling a large amount of shares at an arbitrary single-day price and instead spreads the cost or sale basis out over time. All that said, there's nothing wrong with locking in a gain by selling all or some shares of a winner. Buy low, sell high!" the difference would be taxes...  Lets say you have two lots, one with a 10 dollar gain, and one with a 20 dollar gain.  And lets say you decide to sell one lot this year, and the other lot in 10 years.  AND, lets say that it turns out the stock price is exactly the same in ten years as it is when you sell the first lot. In all likelyhood, you'll have more income, and therefore you are likely to be in a different marginal tax rate.  If you believe that you're more likely to pay more taxes in 10 years, then sell the lot with the higher gain now.  If you believe you're more likely to pay more taxes now, then sell the lot with the lower gain now. No. Not directly. A company issues stock in order to raise capital for building its business. Once the initial shares are sold to the public, the company doesn't receive additional funds from future transactions of those shares of stock between the public.  However, the company could issue more shares at the new higher price to raise more capital. You don't. When you sell them - your cost basis would be the price of the stock at which you sold the stocks to cover the taxes, and the difference is your regular capital gain. "It's impossibly difficult to time the market. Generally speaking, you should buy low and sell high. Picking 25% as an arbitrary ceiling on your gains seems incorrect to me because sometimes you'll want to hold a stock for longer or sell it sooner, and those decisions should be based on your research (or if you need the money), not an arbitrary number. To answer your questions: If the reasons you still bought a stock in the first place are still valid, then you should hold and/or buy more. If something has changed and you can't find a reason to buy more, then consider selling. Keep in mind you'll pay capital gains taxes on anything you sell that is not in a tax-deferred (e.g. retirement) account. No, it does not make sense to do a wash sale where you sell and buy the same stock. Capital gains taxes are one reason. I'm not sure why you would ever want to do this -- what reasons were you considering? You can always sell just some of the shares. See above (and link) regarding wash sales. Buying more of a stock you already own is called ""dollar cost averaging"". It's an effective method when the reasons are right. DCA minimizes variance due to buying or selling a large amount of shares at an arbitrary single-day price and instead spreads the cost or sale basis out over time. All that said, there's nothing wrong with locking in a gain by selling all or some shares of a winner. Buy low, sell high!"