How do I know when to sell a stock?

Start with why you bought it. Every sell decision is the same question asked again: is the reason I bought this still true? A trade is bought for a price move with an exit plan; an investment is bought for a business at a price. They are answered differently, and the most common mistake is switching from one to the other when the price falls.

What you paid does not belong in the answer. The market does not know your entry, and “I will sell when I get back to even” turns a price you happened to pay into a target that has nothing to do with the stock.

Sell discipline
Selling rules written before you buy, so that the exit is a decision made calmly rather than a reaction to the price.

When to sell a stock as a trader: four exits set before entry

A trade has its exits before it has its entry, so the sell decision is made while you are calm and before any gain or loss exists. There are four, and most plans combine two or three of them. UpTickFlow, our TradingView indicator, works the same way: each signal comes with its stop, targets and time limit before the trade.

  • Stop loss: the price that proves the idea wrong, just beyond the level you traded from. When it is hit you sell, and you never move it further away. Stop loss and take profit covers where to place it.
  • Target: the next level where price is likely to stall, often 1.5R to 3R away. You can sell all of the position there or part of it.
  • Trailing stop: a stop that follows the price up and never moves down, used to stay in a trend until it fades; see trailing stop loss.
  • Time stop: if the trade has not done what it was meant to do within a set number of sessions, sell and free the money. A setup that stalls has already failed its own test.
Time stop
An exit rule that sells a position if it has not moved as planned within a set number of sessions, whatever the price.
Trailing stop
A stop that rises as the price makes new highs on a long position and never moves back down.

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A hypothetical XYZ swing trade over 14 sessions. The entry at $40.00, a red stop line at $37.50, a green dashed target at $46.00 and a thin line at $42.50 marking +1R. A dashed vertical line at session 10 is the time stop, with a note that +1R was already reached on session 5. From session 5 an orange trailing stop steps up $2.00 below the highest close, to $43.30 after the $45.30 close. Price falls through it on session 13, where the exit is marked: $43.30, +1.32R. The target is never reached.

When to sell a stock at a loss: how to cut losses

Cut a losing trade when the stop is hit, not when the loss starts to hurt and not when it stops hurting. The rules that make this work are mechanical: put the stop order in at entry, size the position so the stop costs about 0.5% to 1% of the account, never move the stop further away, and do not buy more of a losing trade to lower the average price.

An investment is cut on facts about the business, not on the price alone. Sell when the thesis breaks: the growth you paid for stops, the debt becomes a danger, management changes the story, or the reason you wrote down is simply no longer true. A falling price is a signal to recheck the thesis, not proof that it broke; a broken thesis is a reason to sell even when the price is still above what you paid. If the loss is already large, what to do after a big loss walks through the next steps.

One practical warning about stop orders: a stop order becomes a market order once its price is reached, so in a fast market or a gap the fill can be well below the stop price, as the US regulator FINRA points out. A stop-limit order caps the price but may not fill at all. Plan for the gap case in advance, especially over earnings.

When to sell a stock for profit

For a trader, profit-taking is already in the plan: sell at the target, sell part there and trail the rest, or let the trailing stop decide (scaling in and out covers partial exits). Selling early because a gain “feels big enough” is how traders end up with small wins and full-size losses.

For an investor, a gain alone is not a reason to sell. These are:

  • The valuation has run far ahead of the business: the price now assumes years of growth you do not expect. Valuation ratios help you check.
  • The position has grown too big: a winner that has become a large share of the portfolio adds risk, and trimming it back to its planned weight is rebalancing, covered in portfolio diversification.
  • A better use for the money: a new idea you understand better, with a stronger case, at a better price.
  • You need the money: cash you need within a year or two should not depend on the stock market.

The disposition effect: why we sell winners too early and hold losers too long

Most people do the opposite of the rules above. Economists Hersh Shefrin and Meir Statman named it the disposition effect in 1985: the tendency to sell winners too soon and hold losers too long. In a 1998 study of the trading records of 10,000 accounts at a large US discount broker from 1987 to 1993, Terrance Odean found that investors realised gains at a rate of 14.8% but losses at only 9.8%, so winners were sold about one and a half times as readily as losers.

It also cost them. Over the following year, the winners they sold beat the market by 3.4 percentage points more than the losers they kept. Trading psychology explains the loss aversion behind it. The practical fix is to decide the exits before the trade, when there is no gain or loss yet to protect.

Disposition effect
The tendency to sell winning positions too soon and hold losing positions too long, named by Shefrin and Statman in 1985.

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Two bars from Odean’s 1998 study of 10,000 brokerage accounts, 1987 to 1993: the proportion of gains realised, 14.8%, in green, and the proportion of losses realised, 9.8%, in red. A note says winners were sold about 1.5 times as readily as losers. Underneath, a second note says that over the next year the winners sold beat the market by 3.4 percentage points more than the losers kept.

A sell checklist to write before you buy

Write it on the order ticket or in your trading plan before the order goes in. If a line is blank, the position is not ready:

  1. Why am I buying, in one sentence: a trade setup or an investment thesis?
  2. What would prove me wrong: a price level for a trade, a business fact for an investment?
  3. The stop price, and the dollar loss if it is hit: about 0.5% to 1% of the account for a trade.
  4. The target, or the sign that the trend is over (the trailing stop rule).
  5. The time limit: how many sessions or weeks before I sell a position that has not moved.
  6. For an investment: which results I will check, such as the next two earnings reports, and the valuation at which I would trim.
  7. The largest weight the position may reach in the portfolio before I trim it back.
  8. What I will do if the price gaps through my stop.

A worked example: selling XYZ as a trade and as an investment (hypothetical)

The trade: XYZ is bought at $40.00 as a swing trade. The stop is $37.50, just below the swing low, so 1R is $2.50 a share. The target is $46.00, the next resistance, 2.4R away. The time stop sells if XYZ has not reached +1R ($42.50) within 10 sessions, and once it has, a trailing stop follows $2.00 below the highest close.

XYZ closes at $42.60 on session 5, so the time stop no longer applies and the trail starts at $40.60. After a $45.30 close on session 10 the trail sits at $43.30. The target is never reached: on session 13 XYZ falls through $43.30 and the trail sells, for +$3.30 a share, or +1.32R. No decision was made after entry.

The investment: in a $40,000 portfolio, 100 shares of XYZ at $40 are a planned 10% weight, bought because sales were growing about 20% a year. If two later reports show growth slowing to 3%, the reason is gone, the thesis is broken and the plan says sell, whatever the price. If instead XYZ rises to $70 while the rest of the portfolio stays at $36,000, the position is $7,000 of $43,000, or 16.3%. Selling 39 shares for $2,730 trims it back to 61 shares worth $4,270, or 9.9%.