Taking the short position on a stock you own is called selling short against the box. I don't know much about it, just had heard of it, but it sounds like it's

Taking the short position on a stock you own is called selling short against the box. I don't know much about it, just had heard of it, but it sounds like it's been regulated in the US (to reduce its use for tax avoidance) since 1997. https://www.investopedia.com/terms/s/sellagainstthebox.asp https://www.investopedia.com/terms/s/sellagainstthebox.asp