0DTE Partial In the Money (ITM) Assignment Pin Risk

With the recent rise in the popularity of 0DTE options trading, one decision traders must consider is which ticker to trade. SPX and SPY both offer daily expirations. However, while they’re similar in many ways, they have key differences that could impact your decision.

This article explores a few key advantages of using SPX to avoid assignment when trading 0DTE credit spreads.

SPX vs SPY: What’s the difference?

There are many key differences and similarities in trading SPX and SPY, including settlement, tax rules, fees, and more.

SPX index options are cash-settled at expiration and do not take delivery of shares. This makes SPX particularly attractive to 0DTE traders, as they can close their positions cleanly at expiration without worrying about residual market exposure if they're assigned. SPX is also European-style, meaning there is no assignment risk before expiration.

SPY ETF options settle into physical shares of SPY. If a 0DTE trader is assigned and unwillingly holds a position overnight, they face exposure to price movements that can occur before the next trading session opens. These after-hours moves might be triggered by anything from economic reports to geopolitical developments, and they can lead to substantial, unexpected losses.

Equities and ETFs (like SPY) have physical settlement, meaning traders are obligated to accept 100 shares per contract if assigned or if the short option expires in-the-money (ITM). When trading these securities, the biggest risk is having a credit spread with the short option expiring in the money and the long option expiring out-of-the-money.

How does option assignment work?

The OCC facilitates the assignment process.

For example, if a stock is trading at $100 and you sell a 100 Put, the put buyer has the right to sell 100 shares at $100 any time until the options expire. If the stock is below $100 at expiration,you will be assigned 100 shares per contract and are obligated to purchase stok at $100 .

If a short option expires in-the-money, the broker sends a notice of exercise to the Options Clearing Corporation (OCC). The OCC randomly selects a clearing member firm that is short the exercised contract and assigns the firm the exercised option. The clearing member firm assigns the exercise to one of its customers holding the short option (either randomly or on a first-in, first-out basis). The assigned put writer must purchase the shares to fulfill the obligation of the assignment. The broker then delivers the put writer’s shares to the OCC, who delivers the shares to the broker whose customer initially exercised the put option.

What happens when an option spread expires partially in-the-money (ITM)?

When a short option expires ITM, you are obligated to accept shares. Short puts convert to long stock and short calls convert to short stock. If the long leg is also in-the money, it will be auto-exercised by the broker, and the shares will cancel out.

For example. if your short put is assigned you are long stock at the option's strike price. The long put gives you the right sell the stock. Subtract the spread width from the initial credit received to calculate the max loss.

However, if only the short leg expires ITM, the long option will expire and no longer protect the assigned shares. This scenario puts traders at risk if a large gap occurs overnight before they can exit the position.

Many traders prefer to use credit spreads and iron condors for risk-defined 0DTE option positions, but those trades only maintain their risk profile if both legs expire in-the-money (ITM) and the long leg is exercised.

Spreads that expire partially in the money can lead to significantly greater losses than expected.

It is important to note that most brokers have assignment fees if you hold an ITM position through expiration. Even though SPX options settle to cash, the contracts sill go through the assignment process and incur associated costs.

Avoiding Overnight Risk with SPX

By choosing SPX index options, traders can confidently navigate short-term strategies without worrying about assignment risk. SPX’s cash-settlement system ensures that no lingering exposure could jeopardize the day’s gains once the market closes.

In comparison, traders holding SPY ETF options face the added complexity of potentially managing an overnight stock position, with the possibility of adverse price movements affecting their portfolios before they can react. SPX options provide a more controlled and predictable outcome for those who prefer to avoid this uncertainty.

0DTE traders specifically need to pay close attention to their expiring positions at the end of the day. SPX eliminates the worry of holding shares overnight.

Example: SPX Index vs. SPY ETF – A Comparison of Gap Risk

Consider a practical example and explain how assignment risk differs for SPX and SPY when the option contract expires at the end of the trading day.

What happens when SPX options expire?

• Position: A 0DTE SPX short put spread (short 5580 put, long 5540 put) that expires at the end of the day. 

• At Expiration: If SPX closes above 5,580, the position realizes the maximum potential profit as both contracts expire OTM and worthless. If SPX closes below 5,540, both contracts will expire ITM and will be cash-settled to the maximum loss of the position. However, if SPX closes between 5,580 and 5,540, the short option would expire in-the-money, and the long option would expire out-of-the-money. In this case, we’d have to calculate the net partial profit/loss that gets settled to cash.

• Result: Let’s assume SPX closes at 5,570, and the short put spread received a net credit of $3.00 on entry. The final payout is then calculated as: (5580 - 5570) x 100 = $1,000, less the credit received ($300) = -$700 loss.

As you can see, since SPX settles in cash at expiration, even though the trade loses money, there was no overnight exposure, and the trader has no residual position. You’re not stuck with a partial assingment and underlying shares that can be affected by market movements the next day as is a risk for non-cash settled ticker symbols like SPY.

What happens when SPY options expire?

• Position: A 0DTE SPX short put spread (short 558 put, long 554 put) that expires at the end of the day. 

• At Expiration: If SPY closes above 558, the position realizes the maximum potential profit as both contracts expire OTM and worthless. If SPY closes below 554, both contracts will expire ITM. The short option will be assigned and the long option will be auto-exercised by the broker; the position will realize the maximum loss. However, if SPY closes between 558 and 554, the short option would expire in-the-money, and the long option would expire out-of-the-money. In this case, the short put option would be exercised and the long put option would expire OTM. We would be assigned 100 shares per contract at a price of 558.

• Result: Let’s assume SPY closes at 556. The trader is now long 100 shares of SPY at a price of 558 ($55,800) going into the next trading day. The long 554P expires, and the trader has no option protection; the trade is no longer risk-defined. If any news or events affect the markets overnight, these shares are subject to gap risk, meaning they could open much lower or higher than the previous close.
  
  

If, for example, SPY opens at $550 the next day, the trader faces a loss of -$800 (less the original credit received) since 100 shares would now be worth $55,000. This exceeds any potential max loss the $4 wide position would have had before expiration. Of course, the loss could be even larger if SPY’s price moves more. Furthermore, the cost of carrying the position ($55,800) may be more than the available capital in the account, which could result in broker intervention to liquidate the position.

*Traders should speak with their brokers directly for all information regarding assignment and exercise for different ticker symbols and account types and any associated fees.

Conclusion

While SPX offers some unique advantages to SPY, including cash settlement, European-style contracts, and favorable tax treatment, traders need to decide what is best for them. SPY also includes advantages, such as no exchange fees, commission structure, and more liquidity and daily trading volume.

Traders may also consider XSP, an index option that enjoys many of the same benefits of SPX. XSP trades at 1/10th the value of SPX. However, XSP typically has much lower liquidity than both SPY and SPX.