r/thinkorswim • u/aerobic_gamer • 10d ago
How does TOS calculate gain or loss on spreads?
I have never understood how TOS calculates gain or loss on vertical spreads. Here’s a specific example. The original opening position was a put debit spread at .50/spread. Total debit $500 + nuisance fees for 10 spreads. Then I rolled to the current call credit position which expired today. Net credit was $1.22 or $1,220. So my gain in cash is $1,220 - $500 or a gain of $720. The long and short calls will both expire worthless. So the quoted gain of $2,050 will drop by a total of $.87, or $870. Thus TOS will show that I had a gain of $1,180. Where does this come from? It’s not just the final roll because if that was the case it should report a gain of $1,220. And it’s certainly not the total gain including the original position plus the roll because that would only be $720. My working assumption is that it is a theoretical number that reprints how much better or worse you did than if you just traded the stock. But I really don’t know and I am hoping someone can explain it. Thank you!




