What Is Short Selling?

Borrowing shares to sell them — perfectly legal, deeply strange, fully explained

7 min read Intermediate

"Short selling is borrowing shares you do not own, selling them, hoping the price falls, buying them back cheaper, and returning them. The downside is theoretically unlimited. The upside is capped at 100%. This chapter explains why anyone does it."

For educational purposes only. Nothing in this chapter is financial advice. All figures are illustrative examples. Tax rules, account types, contribution limits, and regulations differ by country and change over time. Always verify current rules with official government sources or a qualified financial adviser before making any investment decisions.

What Short Selling Is

Short selling means borrowing shares you do not own, selling them at the current price, and hoping to buy them back later at a lower price. You return the borrowed shares and keep the difference as profit.

Step by step

Borrow 100 shares of Company X from your broker (you pay a borrow fee).

Sell those 100 shares at £50 each. You receive £5,000.

The share price falls to £35. You buy 100 shares for £3,500.

Return the 100 shares to your broker. Profit: £1,500 minus borrow fees and commissions.

Why the Risk Is Asymmetric — Against You

When you buy a share, your maximum loss is 100% of what you paid. The share can fall to zero. When you short a share, your maximum loss is theoretically unlimited — because there is no limit to how high a share price can rise.

The famous GameStop short squeeze of 2021 illustrated this. Professional short sellers had large short positions in GameStop at ~$20. Retail traders on Reddit coordinated buying that pushed the price to $483. Short sellers faced catastrophic losses to exit their positions.

Who Uses Short Selling and Why

Institutional investors use short selling for two main purposes: speculation (betting a price falls) and hedging (reducing the risk of a long portfolio). A fund with £100m in equities might short £20m worth of individual stocks it believes are overvalued to reduce net market exposure.

Retail investors can access short selling through CFDs, spread betting, or inverse ETFs — each with different risk profiles. Inverse ETFs provide downside exposure without unlimited loss potential but suffer from daily rebalancing decay over time.

FAQs

Is short selling legal?

Yes. It is a legitimate and legal investment strategy regulated in all major markets. Regulators occasionally impose temporary short-selling bans on specific stocks during crises (e.g. financial stocks in 2008).

What is a short squeeze?

When a heavily-shorted stock rises, short sellers rush to buy shares to close positions (cutting losses). This buying pushes the price higher, which forces more short sellers out, creating a rapid price spike. GameStop 2021 is the most famous recent example.

What is the borrow rate?

The fee charged by your broker for lending shares to short sellers. For easy-to-borrow stocks it may be 0.25–1% annually. For hard-to-borrow stocks (heavily shorted) it can reach 50–100%+ annually, making the trade uneconomical.

Can I short inside an ISA?

No. ISAs do not permit short positions, CFDs, or spread betting. Short exposure requires a general investment account or a specialist derivatives account.

Key takeaways

Short selling: borrow shares, sell them, buy back cheaper, return them. Profit = the difference.
Maximum loss on a short position is theoretically unlimited — the price can always rise further.
A short squeeze occurs when rising prices force short sellers to buy, accelerating the move upward.
Retail access: CFDs, spread betting, or inverse ETFs — each with different risk profiles.
Not available inside an ISA.