Just for completeness sake, there are special situations when early exercise makes sense even through option theory tells you otherwise. Usually, these are either related to tradeabily of the underlying vs the option or due to some special features that would not result in adjustment of the options contract but will significantly change the price of the underlying.
When you say short selling,are you referring to a synthetic put position,and the stock becomes impossible to borrow??
I listed in another post when it may make sense to exercise early. What you quoted and responded to was my statement that you should never exercise early if an option has extrinsic value that you could sell it for.
As suspected, here the proof of the above said: Code: CALL S0=5.0000 DTE=60 Pr=0.5000(IV=61.99) rPct=0.00 qPct=0.00 Sx=6.0000 DTE=50 Pr=1.1000(IV=52.64) rPct=0.00 qPct=0.00 Calculations (w/o commissions): Early-Close: PL=0.6000 (120.00% in 10 days --> 1000.36% p.m.) Early-Exercise: PL=0.5000 (100.00% in 10 days --> 723.44% p.m.) Auto-Exercise-at-Expiration: PL=0.5000 (100.00% in 60 days --> 42.10% p.m.) p.m. : per month Early-Closing gives the highest profit, Early-Exercise is 2nd, and Auto-Exercise-at-Expiration gives the least profit. Q.E.D. I even claim that there are much more situations/possibilities/opportunities where an early-close or early-exercise makes more profit than auto-exercise-at-epiration, simply due to the formula "time is money"... These findings (facts) prove "the theory" and many experts wrong...
No, I just mean basic ShortSelling, and closing it before expiration (b/c it cannot generate any more profit b/c with ShortSelling the max possible profit is known in advance... Just simple maths).
A slightly extended output: Code: CALL K=5.00 S0=5.0000 DTE=60 Pr=0.5000(IV=61.99) rPct=0.00 qPct=0.00 Sx=6.0000 DTE=50 Pr=1.1000(IV=52.64) rPct=0.00 qPct=0.00 Calculations (w/o commissions): Early-Close: Pr=1.1000 PL=0.6000 (120.00% in 10 days --> 1000.36% p.m.) Early-Exercise: Pr=1.1000 PL=0.5000 (100.00% in 10 days --> 723.44% p.m.) Auto-Exercise-at-Expiration: Pr=1.0000 PL=0.5000 (100.00% in 60 days --> 42.10% p.m.) p.m. : per month = 1/12 years = 365.00/12 days = 30.416667 days Sometime later I'll do also a brute-force search to find the optimum as I suspect there must be an optimum point in time.
You realize that by exercising, by and large you are giving away a free option with no compensation..