But as I understand it, the Market Makers like Citadel are only required to be market neutral in terms of their statistical exposure at the end of the day, and don't need to report their long/short position. On the other hand, brokers aren't required to be delta neutral, but do report their long/short position. You can probably hide a lot of these shorts in this baby. I guess this also doesn't count short interest that's in bespoke one-off derivatives that hedge funds and investment banks trade between themselves.

Also, nobody has to tell Ortex what their short interest is. The only true numbers we can sort of trust are the twice monthly delayed reports. Ortex is just a third party service provider that goes around calling brokerages and doing some stats on the market to see how they think the short interest has changed.

So, I can see it being pretty low risk even if you do get caught.

I think (with very low probability, but it is an explanation) this could also be why we're seeing random 100% spikes in unrelated stocks that claim to have approximately 0% short interest. Some hedge fund somewhere is in some sort of hidden short, getting margin called, or nervous, or just de-risking and getting out of an off the books short trade, causing a mini short squeeze. There are a couple companies with suspicious pops this week, and I'd be on the lookout for more of this activity on Monday. Could just be people getting out of high volatility positions though, or freeing up capital for other things. But that would be selling pressure, not buying. So, -\?/-