What is Options Writing? Risks, Margin Rules & Strategies

How option writing works — the essentials

Call writer (short call): You sell someone the right to buy the underlying asset from you at a set strike price before expiry. If the option is exercised and you don’t own the underlying, you must deliver shares (or close/offset the position), potentially at large cost.
Example:
Suppose you sell one lot of NIFTY 23,000 Call Option at a premium of ₹50, when NIFTY is at 22,800. You immediately receive ₹2,500 (₹50 × 50 lot size).
If NIFTY stays below 23,000 till expiry, the option expires worthless, and you keep the ₹2,500 profit. But if NIFTY jumps to 23,400, the buyer will exercise the call. You will have to sell NIFTY at ₹23,000, even though it’s trading at ₹23,400. That’s a ₹400 loss per unit, or ₹20,000 loss (₹400 × 50) minus the ₹2,500 premium you earned. Net loss: ₹17,500.

Put writer (short put): You sell someone the right to sell the underlying asset to you at the strike price before expiry. If exercised, you must buy the shares at that strike, even if market price is much lower.
Example:
You sell one lot of RELIANCE 1,400 Put Option at a premium of ₹10, when the stock is trading at ₹1,420. You collect ₹10 × 550 (lot size) = ₹5,500 upfront.
If the stock stays above ₹1,400 till expiry, the put option expires worthless, and you keep the ₹5,500 profit. But if RELIANCE falls to ₹1,300, the buyer will exercise the put.You’ll have to buy shares at ₹1,400, even though the market price is ₹1,300. That’s a ₹100 loss per share, or ₹55,000 loss (₹100 × 550) minus the ₹5,500 premium. Net loss: ₹49,500.
Profit for a writer is limited to the premium received; losses can be large (and theoretically unlimited for uncovered calls). Because of this asymmetry, exchanges and brokers require margin to ensure obligations can be met.
 

Key risks of writing options

1. Unlimited or large downside (naked calls): Selling uncovered calls exposes you to theoretically unlimited loss if the underlying rallies sharply.

2. Large capital commitment (naked puts / assignment risk): Selling puts can result in being assigned and forced to buy large quantities of stock at the strike, tying up capital and possibly realizing large paper losses.

3. Margin/mark-to-market (MTM) shortfalls: Written positions are marked to market daily; adverse moves create margin calls. If you can’t meet margin calls, your broker can square off positions at potentially worse prices.

4. Volatility & gap risk: Sudden spikes (earnings, macro news) can blow through strikes and result in rapid losses before you can hedge or close positions.

Margin rules in India — what you must know

Exchanges and clearing corporations in India use a risk-based margin framework. The two primary margin components for F&O positions are:

SPAN margin: A portfolio-level, scenario-based minimum computed using the SPAN engine (Standard Portfolio Analysis of Risk). SPAN is the basic margin everyone must maintain to initiate trades.

Exposure (or extreme loss) margin: An additional percentage buffer charged over SPAN to cover extreme one-day losses that SPAN may not capture. For index short options, exchanges often levy an extra 2% as an extreme-loss margin; for stock options the exposure margin is commonly set higher (brokers/exchanges vary).

Practically, initial margin = SPAN + exposure. Brokers publish calculators and examples; numbers change with volatility, contract value and lot size, so always check your broker’s margin calculator before writing options. Also note exchanges expect brokers to collect a minimum upfront portion (exchanges/clearing norms require brokers to collect specified minimum upfront margins).

Typical exposure guidelines used by many brokers (indicative, subject to change): index option selling exposure ≈ 2% of contract value; stock option selling exposure ≈ 1.5–3.5% of contract value. These are additive to the SPAN computed by the exchange. Always use the exchange or broker’s live margin tool for exact numbers.

Who should consider writing options?

• Investors seeking extra income from existing long stock positions (covered calls).
• Traders with sufficient capital and risk controls who understand assignment, margin, and exit mechanics.
• Sophisticated traders using multi-leg spreads to limit risk while capturing premium.

Retail beginners should avoid naked selling until they understand margin behavior, MTM, assignment, and have contingency capital for margin calls.
 

Practical strategies (simple, effective)

Covered Call (buy stock + sell call): Conservative income strategy. Own the stock and sell call(s) against it to earn a premium. Upside is capped at strike + premium; downside still exists but premium provides a small buffer. Well-suited for mildly bullish-to-neutral views.

Cash-Secured Put (sell put + hold cash): Sell put options while keeping enough cash to buy the underlying if assigned. Generates income and can be a way to acquire stock at a lower effective price. Requires capital to cover potential assignments.

Vertical Spreads (bear call / bull put spreads): Sell one option and buy another further out-of-the-money to cap risk. Spreads reduce margin and limit maximum loss at the cost of lower maximum profit. Good for defined-risk sellers.

Iron Condor / Iron Butterfly: Combine calls and puts to create a range where you collect premium and profit if underlying stays within a band. These are more advanced and require active risk and margin management.

Execution checklist — before you write any option

• Check SPAN + exposure required for the exact contract and lot size with your broker or the NSE margin calculator.
• Decide if position will be covered (own stock/cash) or naked (higher margin and risk).
• Use defined-risk strategies (spreads) when in doubt to limit worst-case loss.
• Have a plan for margin shortfalls: add funds, hedge, or close positions quickly.

Conclusion

Options writing is a powerful way to generate income, but it shifts asymmetric risk to the seller. The mechanics are simple—collect premium today in exchange for a future obligation—but the margin framework and assignment rules make prudent capital and risk management essential. In India, SPAN and exposure margins (exchange/broker-calculated) determine how much capital you must park to write options; typical exposure rules (e.g., ~2% for index options) are additive to SPAN. For most investors, covered calls and cash-secured puts are responsible starting strategies, while spreads give defined risk for more active sellers. Always check live broker/exchange margin tools and understand daily MTM before you write options.