After speaking with OptionsHouse this morning, I finally understand what was going on. Indeed, I could have been on the hook for a boatload of money.
My confusion was due to the fact there are two settlement types,
cash and physical. SPY is physical settlement meaning I take possession of the ETF shares if assigned, whereas cash settlement would be just that. No stock ETF shares would change hands. SPX is cash settlement and with SPX, the loss is truly limited by the spread.
I have been trading SPX and RUT for the last three years and only tried the SPY in the past month, so I was not familiar with the physical settlement methods.
So a good lesson learned, and I shall go back to cash settlement indexes for my credit spreads.
As for the critics here of my method of trading, understand that credit spreads aren't for everyone. Risk reward is upside down, but risk reward ratio of 5% to 95% also equates to 95% success rate. And when you learn to manage the losers to limit your loses, you have a system with a nice little side income.
Happy trading everyone! (except maybe drownpruf)
