Stock Borrow Fee: What It Costs to Short a Stock

A stock borrow fee is the cost a short seller pays to borrow shares before selling them. It is quoted as an annualized percentage of the borrowed position's value and accrues daily for as long as the position stays open. Easy-to-borrow stocks cost little; scarce, heavily shorted stocks can cost far more.

This page is for traders and curious investors who want to understand the real cost side of short selling before trying it. If you have ever seen "hard to borrow" or a surprising interest charge on a brokerage statement, this explains where that number comes from. Read the mechanics, run the worked example, and use the decision framework before you commit to any short position. Everything here is educational, not financial advice.

What a stock borrow fee is

When you short a stock, you sell shares you do not own. To deliver those shares to the buyer, your broker first has to borrow them from someone who does own them. That loan is not free. The share owner, usually a large institution, lends the shares out in exchange for a fee, a practice regulators describe in the SEC's securities lending overview. Lenders include mutual funds, ETFs, pension funds, and brokers lending their own or customers' shares.

The borrow fee, sometimes called the borrow rate or stock loan fee, is how that cost reaches you. Your broker passes it through to your account, typically as a daily charge against the value of the shares you have borrowed. You pay it whether your short trade wins or loses.

Why borrow fees exist: how short selling works

The fee makes more sense once the full loop is visible. As the SEC describes it in its short sales overview, a short sale is the sale of a security the seller does not own. The seller borrows the security, usually through a broker-dealer, delivers it to the buyer, and later closes the position by purchasing equivalent shares on the open market and returning them to the lender.

Every day between the borrow and the return, someone else's property is on loan to you. The lender wants compensation for giving up the shares, for taking on counterparty risk, and for losing the chance to lend them to someone else. Supply and demand set the price of that loan. When plenty of shares are available, the fee stays low. When many short sellers chase a small pool of lendable shares, the fee climbs.

How borrow fees are quoted and charged

Borrow fees are quoted as an annualized rate but charged in daily slices. The basic math looks like this:

1. Take the market value of the borrowed shares, often based on the closing price.
2. Multiply by the annualized borrow rate.
3. Divide by 360 or 365, depending on the broker's convention.
4. That result is the charge for one day.

Here is a hypothetical illustration. Suppose you short 200 shares of a stock at $50, a $10,000 position, and the borrow rate is 6% annualized. One day costs roughly $10,000 x 0.06 / 360, or about $1.67. Hold for a month and you have paid around $50. If the rate were 60% instead, that same month would cost around $500, five percent of the whole position, before the stock even moves.

Two caveats matter. First, the rate is not fixed: it can change daily with lending supply and demand, so the fee you start with is not the fee you are promised. Second, the charge is based on the position's current value, so a rising stock price increases both your paper loss and your daily fee.

What makes a stock hard to borrow

Lendable supply and short-selling demand divide the market into two broad groups:

Stocks become hard to borrow when short demand is intense, when the float is small, when many holders keep shares in accounts that do not lend, or around events like IPO lockup expirations and merger arbitrage situations. Popular "battleground" stocks with high short interest are the classic case: everyone wants to borrow the same limited shares, and the fee auctions itself upward.