Wasting asset

Buy a share and do nothing. A month later you still own the share. Buy an option and do nothing, and a month later you may own nothing at all.

That is what "wasting asset" means. An option premium has two components — intrinsic value, which is the amount by which it is already in the money, and time value, which is what you pay for the possibility that it moves further in your favour before expiry. On expiry day there is no more "before expiry". The time value is zero, necessarily, because there is no time left.

So the time value portion of every option premium is structurally biased downwards. It erodes a little every day, faster as expiry approaches, and reaches zero on the last day whatever happens. The workbook puts it starkly: if all other things remain constant throughout the contract period, the option price will always fall by expiry.

The Greek that measures the erosion is theta — the change in an option's price for a one-day decrease in time to expiration. Theta is negative for a long option, call or put alike: other things being equal, options lose time value every day of their life.

The consequence the workbook draws is the one candidates under-rate: option sellers are at a fundamental advantage compared with option buyers, because there is an inherent tendency in the price to go down. The seller is not merely betting against the buyer's direction; he also collects the decay while he waits.

Time value is largest when there is most time and most uncertainty left, which is why a longer-dated option always costs more than a shorter-dated one with the same strike, and why higher volatility raises the premium of calls and puts alike.

Only the time value wastes. An in-the-money option keeps its intrinsic value to the last, provided the underlying stays where it is — which is why the decay bites hardest on an out-of-the-money option, whose premium is entirely time value.

Option premium = Intrinsic value + Time value

Theta = Change in option premium ÷ Change in time to expiry

At expiry:  Time value = 0,  so  Premium = Intrinsic value

The index stands at 17,450. A trader buys the 17,600 call with five days to expiry at a premium of Rs 42. Lot size 50.

Outlay          = 42 × 50 = Rs 2,100
Intrinsic value = 0        (the strike is above the index — out of the money)
Time value      = Rs 42    ← the entire premium

The option quotes a theta of 8.40, so it loses Rs 8.40 a day. Suppose the index goes absolutely nowhere and sits at 17,450 for five days:

The index did not move by a single point and the buyer lost 100% of his money. The trader who sold him that call keeps the whole Rs 2,100.

Now the in-the-money contrast. Same index at 17,450, but the 17,300 call trades at Rs 196:

Intrinsic value = 17,450 − 17,300 = Rs 150   → Rs 7,500 per lot
Time value      = 196 − 150      = Rs  46   → Rs 2,300 per lot

If the index again sits still to expiry, only the Rs 2,300 of time value wastes away. The Rs 7,500 of intrinsic value survives and is settled. Same index, same stillness, same five days — Rs 2,100 lost on one contract, Rs 2,300 lost on the other, but one buyer walks away with Rs 7,500 and the other with nothing.

Chapter 4 (Introduction to Options) introduces the term while discussing time to expiration as a determinant of the option premium, and then formalises the erosion as theta under the Option Greeks. Chapter 10, section 10.1, repeats it as a risk to be disclosed to clients: "Options are a wasting asset", and if the underlying does not move in the anticipated direction the buyer risks losing the entire premium in a short span of time. Expect the direct question "options are described as wasting assets because ___", the theta computation, and the conceptual point that the option seller has a structural advantage.

• Only the time value wastes, not the whole premium. An in-the-money option retains its intrinsic value at expiry. The blanket statement "an option is worth nothing at expiry" is wrong.
• Theta is negative for long options, both calls and puts. Decay is not a call-only phenomenon and does not depend on direction.
• Time decay accelerates towards expiry. It is not linear in reality; the workbook's per-day illustration is a simplification for computation, not a claim about the shape of the curve.
• Longer maturity means a higher premium, because there is more time value to lose. Candidates reverse this.
• "Wasting asset" is about time, not about price. The buyer above lost everything without the index falling.
• The seller's advantage is structural, not a free lunch. He gains the decay and carries unlimited risk in exchange, and he alone posts margin.
• Do not confuse the wasting of time value with a futures position, which has no time value and does not decay.