How come my short vertical put has negative theta?

[solk]

If

Skew... ATM doesn't have the highest theta... it's more like this:

you look at the option chain I've posted, you can see that it is linear in the same direction both for calls and puts.

 

[Kim Klaiman]

Fact is, that the vertical call has a positive theta. I am not saying "it has to be" I am saying that thats the way I observed it. Question is, how come selling a vertical put will be theta negative?

Selling vertical put can be theta negative if it is close to ATM. If it is ITM, it is usually theta positive.

For example (using same underlying and expiration, SPX and Sep14, SPX at 2443):

Selling 2445/2415 put credit spread has negative theta (same as buying 2415/2445 call debit spread).

Why this is happening? Because 2445 put has less theta than 2415 put, as you can see from the posted screenshot.
To get positive theta, you would need to go to something like 2410/2390 put credit spread (or 2390/2410 call debit spread).

Again, it's all about the strikes you select.

 

[solk]

Selling vertical put can be theta negative if it is close to ATM. If it is ITM, it is usually theta positive.

For example (using same underlying and expiration, SPX and Sep14, SPX at 2443):

Selling 2445/2415 put credit spread has negative theta (same as buying 2415/2445 call debit spread).

Why this is happening? Because 2445 put has less theta than 2415 put, as you can see from the posted screenshot.
To get positive theta, you would need to go to something like 2410/2390 put credit spread (or 2390/2410 call debit spread).

Again, it's all about the strikes you select.

If that so, butterfly or iron fly is much better composed without the put side, that is - selling call spread on one side and hedging with futures on the other side, because writing a vertical put will just remove from the theta of the call spread instead of increasing it.

 

[Kim Klaiman]

If that so, butterfly or iron fly is much better composed without the put side, that is - selling call spread on one side and hedging with futures on the other side, because writing a vertical put will just remove from the theta of the call spread instead of increasing it.

Not necessarily. It also depends on strikes you use.

For example, selling ATM strikes and buying far OTM strikes will usually produce decent positive theta. Selling OTM strikes will reduce the positive theta and also make the fly more directional.

Hedging with futures will sometimes produce better theta, but it also produces a completely different P/L profile.

 

[stepandfetchit]

Selling vertical put can be theta negative if it is close to ATM. If it is ITM, it is usually theta positive.

For example (using same underlying and expiration, SPX and Sep14, SPX at 2443):

Selling 2445/2415 put credit spread has negative theta (same as buying 2415/2445 call debit spread).

Why this is happening? Because 2445 put has less theta than 2415 put, as you can see from the posted screenshot.
To get positive theta, you would need to go to something like 2410/2390 put credit spread (or 2390/2410 call debit spread).

Again, it's all about the strikes you select.

Solk:
You need to comprehend Kim's statement beginning with "Why is this happening? ..."! It appears you don't understand. This is basic math as Kim clearly stated.

 

[Kim Klaiman]

Here is another factor to consider: being negative theta today doesn't necessarily mean it will stay negative till expiration.

For example, the same 2445/2415 put credit spread (with SPX at 2443) will have negative theta today, but the theta turns positive at some point (around 11 DTE). So it is not necessarily a bad trade - if you believe SPX will stay at 2443 or higher by expiration, the trade will still make money even while starting theta negative.

 

[JackRab]

Jack:
Can you explain how "Skew" shifts the minimum Theta (for PUTs) lower than ATM? The picture you posted incorrectly implies the minimum Theta is ATM, and we can observe the minimum Theta is at a lower strike than ATM (20-30 points lower on the Expiration identified). It would be educational to gain a better understanding of this, and perhaps how this relationship morphs over the years with the market conditions. This post has piqued my curiosity. {I think you are correct, it is due to Skew, but wrestling with getting my head around it}

Skew means that vols are higher for lower strikes compared to ATM and usually calls... at least, this is the case for equities and equity indices. This has to do with downward risk perception.

A higher vol means higher value of an option... therefore increasing theta (value loss due to 1 day time). The pic I put on actually shows the top of the curve is slightly left of the ATM... hardly visible, but it should be there.

The way theta is shown in IB and in general... is wrong IMO. I regard theta as loss in value in 24 hrs... the theta in a call and put of the same strike are exactly the same. However, you notice that in your system, IB or any really, that the theta for calls are higher than for puts. This is due to the fact that options are priced on fwd/future pricing, taking into account an interest factor. So... part of the theta is due to the decrease in interest component... for calls this is a negative number (so increasing theta) and for puts this is a positive number (decreasing theta). IMO this isn't really theta, but just interest component (not to be confused with Rho, that's something else again).

So, usually in options you will see a non-normal distribution, partly due to skew... this causes relative vols and prices in OTM puts to be higher than OTM calls... and this causes that shift in theta to be higher in OTM puts.

 

[JackRab]

Original post: "short vertical put will always have negative theta while a short vertical call will have positive theta."

My comment: "It is not matter of calls or puts, it is matter of strikes."

Which means that short vertical put can have positive or negative theta (depending on the strikes), and short vertical call also have positive or negative theta (depending on the strikes).

Usually a 2435-2425 short putspread, short 35 long 5, would have a positive theta because you are short the nearer ATM and long the more OTM. However, due to skew and how options are priced... this putspread has a negative theta... which OP finds weird, since you would expect it to have a positive theta...

All things equal, PS still being OTM, x days in the future it will be a positive theta...

 

[solk]

Skew means that vols are higher for lower strikes compared to ATM and usually calls... at least, this is the case for equities and equity indices. This has to do with downward risk perception.

A higher vol means higher value of an option... therefore increasing theta (value loss due to 1 day time). The pic I put on actually shows the top of the curve is slightly left of the ATM... hardly visible, but it should be there.

The way theta is shown in IB and in general... is wrong IMO. I regard theta as loss in value in 24 hrs... the theta in a call and put of the same strike are exactly the same. However, you notice that in your system, IB or any really, that the theta for calls are higher than for puts. This is due to the fact that options are priced on fwd/future pricing, taking into account an interest factor. So... part of the theta is due to the decrease in interest component... for calls this is a negative number (so increasing theta) and for puts this is a positive number (decreasing theta). IMO this isn't really theta, but just interest component (not to be confused with Rho, that's something else again).

So, usually in options you will see a non-normal distribution, partly due to skew... this causes relative vols and prices in OTM puts to be higher than OTM calls... and this causes that shift in theta to be higher in OTM puts.

Great and detailed answer. I am trying to understand how to apply this logic to actual trading, knowing the put verticals are theta negative in some cases - that is, when trading butterflies or straddles

 

[JackRab]

Great and detailed answer. I am trying to understand how to apply this logic to actual trading, knowing the put verticals are theta negative in some cases - that is, when trading butterflies or straddles

That's why options are more interesting than plain and straightforward stocks... it's like a box of chocolate, you never know what you're gonna get!