Stock splits, bonuses, dividends, buybacks, mergers — all can change your option contract's terms mid-flight. The exchange adjusts strike, lot size, or both. Understanding these adjustments prevents nasty surprises.
NSE F&O contracts are adjusted for:
Regular quarterly/annual dividends below a threshold do NOT trigger adjustments (the drop is priced in normally).
The contract value must remain the same post-adjustment as pre-adjustment.
Adjustment factor = (Number of new shares) / (Number of old shares)
New strike = Old strike × (1 / Adjustment factor) New lot size = Old lot size × Adjustment factor
Reliance stock: ₹3,000. Lot size: 250. Strike: 3,000. Premium: ₹100.
Reliance announces 1:1 bonus (one new share per share held).
Post-bonus:
Total notional value unchanged: 1,500 × 500 = 7,50,000 = same as 3,000 × 250 = 7,50,000.
Your premium value should also adjust proportionally.
Same idea:
Infosys at ₹1,800. Lot 400. Strike 1,800.
2:1 split announced (one share becomes two).
Post-split:
Contract value: 900 × 800 = 7,20,000 = same as 1,800 × 400.
If the split ratio doesn’t produce clean numbers, exchanges may adjust differently:
3:2 stock split example:
NSE handles fractional strikes by rounding, or issuing “adjusted” contract series with different labels.
Regular dividends (₹5-40 per share range) are typically small enough that no adjustment is made. The stock simply drops by the dividend amount on ex-date, and options price this in normally.
Special dividends (extraordinary, one-time payouts) DO trigger adjustments:
The most complex adjustments. Depends on scheme details:
Each case is unique. NSE publishes detailed circular per event.
1. Monitor corporate action calendars for your positions:
2. Close positions before ex-date if you’re not comfortable:
3. If holding through the event:
Sometimes stocks approach a strike right around the ex-date. If assignment happens on the last day pre-ex-date, you may end up delivering (or receiving) shares that are about to be affected by the corporate action — creating awkward accounting.
Best practice: don’t hold expiry-week options through a scheduled corporate action.
Company announces a share buyback at fixed price. Retail participation is limited. Effect on options:
Not usually a major factor for options traders, but worth awareness.
| Event | Frequency | Option impact |
|---|---|---|
| Stock split | 1-3 per year across F&O stocks | Strike + lot adjust; total value preserved |
| Bonus issue | Occasional | Same adjustment |
| Regular dividend | Quarterly/annual | Priced in; no adjustment |
| Special dividend | Rare; e.g., Coal India specials | Strike reduced by dividend amount |
| Buyback | Occasional | Usually no adjustment; some premium impact |
| Merger | 1-5 F&O stocks per year | Complex; case-by-case circular |
| Demerger | Very occasional | Strike split between entities |
Before an ex-dividend date, put-call parity shifts:
C + K × e^(−rT) = P + S − D × e^(−rt_div)
Where D = expected dividend, t_div = days to ex-date.
Impact:
In the days leading to ex-date, the call-put IV difference widens. This is embedded in prices, not free lunch.
For a deep-ITM American call before ex-dividend:
If dividend > remaining time value of the call, rational exercise happens.
Practical impact for Indian stock option sellers: if you’re short a deep-ITM call and dividend is ~equal to remaining time value, you may be assigned early — a day or two before ex-date. You’ll deliver shares AND miss the dividend.
Mitigation: roll ITM shorts before ex-date if you don’t want assignment.
Options markets sometimes over-price expected dividends:
Trade: if you have insight into dividend uncertainty (analyst estimates diverge), consider trading the mispricing.
Retail: rarely worth the fees. Institutions do this frequently.
Company X announces ₹500 buyback vs ₹450 stock price → limited retail participation, but:
Trade implication: if you own long calls and a buyback is announced, consider closing — your upside is throttled.
Company A being acquired by Company B at ratio 1:2 (holders of 1 A share get 2 B shares).
Options impact:
But — timing matters. Between announcement and effective date, A options often become illiquid; spreads blow out. Consider closing rather than holding through.
Company A acquired for ₹X cash per share.
Options impact:
Practical: if you’re holding options during a cash acquisition, exit immediately after announcement. Uncertainty around timing and exact terms makes holding painful.
Company A demerges Business Unit B (creates new listed entity B).
Options impact:
NSE publishes exact treatment per case. Always read the circular.
Each case unique. Never assume; always check.
Don’t enter a short strangle expecting the “dividend gap fill.” The gap is priced in; there’s no free money. What you can trade is your view on:
Reliance pays ₹8 dividend on ₹3,000 stock. Ex-date impact:
If you don’t want to deal with corporate action adjustments:
This is what most retail traders do. Index options avoid 95% of corporate-action headaches.
NSE Circular section (nseindia.com → Circulars → F&O Segment). Search for “Adjustment” or the stock symbol. Details of every past adjustment are documented.