Can you trust the "last" price in Think or Swim when looking at spreads?

[FrankTheTank]

 

Can you trust the "last" price when looking at historical option spread prices? Using Think or Swim (ToS) I can pull up a market depth window (see image below) and it shows a "last" column which I assumed meant the last filled price for that spread but the prices do not make sense.

In the example below this was for a short Iron Condor with $1 wide wings so max. loss should be $1 less the credit received. If people are really getting more than a $1 credit for selling this position that would be risk free which does not make sense? Thanks.

 

When I saw some people were getting filled for more than $1 I got hopeful and entered  STO at 0.90 which was never filled even though the last column kept showing prices more than $1  (image of my order is below).   Is it possible market makers are getting these prices or ToS is somehow merging each filled price from each leg separately and creating a pseudo last price for this Iron Condor?  

 

 

 

[craigsmith]

@frank the tank This isn't specific to TOS, I've used IB for years and see the exact same thing. The LAST is almost always the MID and I know that isn't correct. The MID is calculated from the individual legs, so that number can be pretty far off also when trying to get filled. The PnL showing on the individual trades is not even close most days.  

 

It's frustrating but just shows how much work you need to put in sometimes to get better results. For example, when I get an instant fill, I know I've probably left a few bucks on the table. 

[FrankTheTank]

3 hours ago, craigsmith said:

@frank the tank This isn't specific to TOS, I've used IB for years and see the exact same thing. The LAST is almost always the MID and I know that isn't correct. The MID is calculated from the individual legs, so that number can be pretty far off also when trying to get filled. The PnL showing on the individual trades is not even close most days.  

 

It's frustrating but just shows how much work you need to put in sometimes to get better results. For example, when I get an instant fill, I know I've probably left a few bucks on the table. 

Thanks.  This is what I figured but you are the first person to actually confirm my suspicions.   I wonder if its even possible to see actual last filled prices like you can for regular stock trades?  I would think/hope that if its possible the brokers would show this instead of the mid price.    I know CBOE sells time and sales data for each trade but it is rather expensive.  

 

[TrustyJules]

In TW there is a quote last function that shows the last trade - whether it is accurate or not I dont know. Closing times and particularly on Friday when the market is moving about a lot spreads widen and you can get weird results, When I use One I tend to go for modelling based on quotes NOT at the end of the day.