T+1 Rules and Short-Sale Arbitrage

Article BigQuant

Summary

This article explains a proposed arbitrage mechanism involving Chinese A-shares, stock purchases, securities borrowing, and short sales. Its example describes buying shares to push the price higher, borrowing shares to sell at that higher price, and later using held or repurchased shares to return the loan. It also outlines a more aggressive version in which the buyer sells its holdings on the following day and seeks to repurchase shares after a price decline. The piece argues that a change requiring borrowed shares to be sold no earlier than the next day would disrupt the timing that the strategy depends on.

The article frames the practice as exploiting differences between retail T+1 trading and institutional access to short selling, and discusses the possible effects of concentrated trading on price volatility. It predicts that restrictions could prompt strategy unwinds, while acknowledging that the scale and duration of any resulting market impact are uncertain. These are the article’s claims and scenario descriptions; it provides no transaction records, quantitative analysis, or independent evidence that the described behavior was widespread or caused institutions to exit. The mechanics and regulatory details should therefore be treated as an account to evaluate, not verified market findings.

Key ideas

The article describes a proposed strategy that combines share purchases with borrowed-share sales to exploit timing differences.
It presents a second version involving next-day selling followed by repurchasing after a price decline.
The author argues that a T+1 restriction on selling borrowed shares would break the strategy’s timing advantage.
It warns that concentrated unwinds could affect volatility but says their scale and duration are uncertain.
The article provides no quantitative evidence verifying how common the described trades were.

How A-Share T+1 Rules Affect a Proposed Short-Sale Arbitrage

Summary

Key ideas

Tags