How to Short a Stock
To short a stock, borrow the shares through a margin account and sell them, with the intention of buying them back later at a lower price. The borrow costs a daily fee, can be recalled at any time, and the potential loss is not capped the way a long position's is.
Video: Michael Whitman on YouTube, a news video on a well-known investor's short position in AI stocks. Watch it on YouTube.
Shorting means borrowing shares, selling them, and buying them back later. If the price falls you keep the difference. Everything difficult about it comes from the borrowing: it costs money daily, it can be withdrawn, and the position it creates has no natural limit on its losses.
Before you start
A margin account, because shorting requires borrowing the shares. A standard cash account cannot do it, and the account terms govern what happens when things go wrong.
The borrow cost, which is charged daily and varies enormously. On a widely held name it is negligible; on a heavily shorted one it can exceed any plausible gain.
An acceptance that the loss is not bounded the way a long position’s is. A share bought at 40 can fall to zero. A share sold short at 40 can rise to 200.
The steps
1. Check the borrow is available and what it costs
Your broker shows availability and rate. A name that is expensive to borrow is expensive because everybody wants to short it, which is information about the trade.
2. Size for an unbounded loss
Take the stop distance and size from it as usual, then take a smaller position than that arithmetic suggests. The gap between the two is the premium for an outcome with no ceiling.
3. Place the stop above a structural level
Check the stock’s average true range first, because a stop inside its ordinary daily movement is noise. Above the swing high that would invalidate the idea.
4. Account for the daily cost in your horizon
A high borrow rate held for months can exceed the fall you were expecting. The cost turns a slow correct call into a losing trade, and that arithmetic belongs in the plan.
5. Know that the shares can be recalled
If the lender wants them back and no replacement can be found, your position is closed at the market price on their schedule. There is no appeal and no warning.
6. Remember dividends run against you
The shares are borrowed, so any dividend paid is owed by you to the lender. On a high-yielding name held across several payments that is a substantial recurring cost.
7. Cover on the plan, not on the panic
Both exits written before entry: the target and the invalidation. A short position moving against you generates more pressure to improvise than any other trade type.
How to tell it worked
The borrow rate was checked before entry, in every case.
Position size was smaller than the stop-distance arithmetic alone would give.
The stop sat above a structural level, more than 1 average bar range clear of noise.
And 0 trades were held past their written invalidation.
Why the asymmetry matters so much
A losing short grows. As price rises, the position’s value against you increases, so the exposure is largest exactly when it is going worst. A losing long shrinks as it falls.
Which means the position size you started with is not the position size you have. That is the mechanical reason short positions require more conservative sizing rather than merely more conviction.
The base rate runs against you
Since 1950 the S&P 500 has finished higher over 59% of ten-trading-day windows and on 53% of single days. A short position starts slightly behind before anything else is considered.
And the borrow cost compounds that. A position that needs price to fall, in a market that drifts up, while paying a daily fee, has three things to overcome rather than one.
None of which makes shorting unreasonable. It makes the edge required larger — the setup has to be better than the equivalent long, not merely as good.
Alternatives that cap the loss
A put option risks only the premium. It expires, which a short position does not, and it costs money up front rather than earning it — but the maximum loss is known at the moment of entry.
An inverse fund moves opposite an index without borrowing. It carries its own problems, chiefly that daily rebalancing makes multi-day returns diverge from the index’s inverse, but nothing about it can lose more than the amount invested.
Neither is a straight substitute. The put has a deadline the short does not, and the inverse fund tracks an index rather than a company.
They are worth knowing about because the bounded loss is the whole point. A stock shorted at $20 that rises to $60 has cost twice the original position, and nothing caps the price — an open-ended loss is exactly what an unbounded short can produce, and both of these alternatives put a floor under it.
The original data
Of the 24,971 unique videos collected for this site’s search study, 14 mention short selling or shorting in the title, at a median of 26,271 views across 14 channels, and 64% of those titles are instruction-shaped. Short squeezes and margin appear in similarly small numbers. Each video is counted once, even when several searches returned it.
14 videos at a 26,271 median. Almost no coverage and a large audience per video — a subject a great many people want explained and almost nobody teaches, which is the shape this site exists to fill.
The question: The short is 20% against you and the thesis is intact. Add?
The answer is that adding increases an exposure that is already larger than you chose. A losing short grows on its own — the position is bigger than when you opened it, and adding to it compounds the one property that makes shorting different.
When it fails
The failure is adding to a losing short, and it is the mechanism behind most of the large losses in this trade type. Price rises, the thesis still looks right, and the higher price makes the short better value. So more goes on. Price rises again. The position is now several times the original size, in a trade whose exposure was already growing by itself, in an instrument that other shorts are being forced to cover — which is what makes the move accelerate rather than stop.
The second failure is ignoring the borrow cost. It can exceed the fall.
A third is sizing by analogy to a long. The loss profile is not symmetrical.
A fourth is forgetting the dividend. You pay it while short.
A fifth is assuming the position is yours to close. It can be recalled.
And a sixth is shorting a hard-to-borrow name. The cost is telling you something.
Related
Short selling covers the mechanism in detail. Short squeeze is the specific failure mode. And margin account is what the whole position runs inside.
Sit with the asymmetry before doing it once. A long position can lose what you put in; a short position can lose several times that, because there is no upper bound on a share price. Choose the size with that in mind rather than by analogy to a long.
— Michael Whitman
This page is educational, not financial advice. Test every idea on your own charts before risking money.