https://www.fool.com/investing/2021/01/28/yes-a-stock-can-have-short-interest-over-100-heres/
Round and round shares go
At first glance, it might seem like you could never have more than 100% of a company's shares sold short. Once all the shares have been borrowed, you might think there wouldn't be any more for short-sellers to get.
Indeed, there are
U.S. Securities and Exchange Commission regulations designed to prevent what's known as "naked" short selling. With a naked short sale, the broker allows the customer to do a short-sale transaction without actually arranging to borrow the shares beforehand. This can lead to market disruptions, and while there are some exceptions to the regulations, most brokers stop regular retail customers from selling stock short if they can't obtain shares to borrow.
However, even without a naked short sale, it's theoretically possible for short interest to exceed 100%. The reason has to do with the nature of the short-sale transaction itself.
As an example, take a situation involving four investors. Annie owns shares of GameStop, and Annie and her broker have an agreement that allows the broker to lend Annie's shares to short-sellers. It lends them to Bob, who subsequently sells those borrowed shares short in hopes that GameStop's share price will fall.
An investor named Chris ends up buying those borrowed shares from Bob. However, Chris has no way of knowing that those shares have been borrowed from Annie. To Chris, they're just like any other shares.
More importantly, if Chris has the same kind of agreement, then Chris's broker can lend out those shares to yet another investor. Diane, another GameStop bear, can borrow those shares and sell them short.
In this example, the same shares end up getting borrowed and sold twice. The short interest volume these transactions add to the total is twice the number of shares actually involved. You can therefore see that if this happened throughout the market, total short interest would eventually exceed the number of shares outstanding and approach 200%.
This still might seem impossible, and in a sense, it is. But part of the answer lies in the fact that there are investors that don't currently possess actual
shares of GameStop but who have the same economic interest as shareholders. They have the right to get back the shares they lent at any time. When you add together the actual shares
plus these "synthetic" positions in the stock, the short interest can't exceed 100% of that larger total.