Understand circuit filters and ban periods in F&O

6.7.13 · Stock-Market › Indian Market Specifics

Overview

Circuit filters aur F&O ban periods regulatory safeguards hain jo SEBI aur exchanges (NSE/BSE) dwara implement kiye jaate hain taaki extreme price volatility aur excessive speculation ko roka ja sake. Ye speed bumps ki tarah kaam karte hain jo trading ko restrict karte hain jab prices bahut tezi se move karein ya jab derivative positions dangerously badi ho jaayein.

Circuit Filters (Price Bands)

Circuit Filter Categories

Indian exchanges ek multi-tier system use karte hain:

Lower Circuit Limit: $P_{\text{lower}}=P_{\text{prev}}\times \left(1-\frac{CF}{100}\right)$

Jahan:

• $P_{\text{prev}}$ = Previous day's closing price
• $CF$ = Circuit filter percentage (5, 10, ya 20)

First principles se derivation:

Circuit filter concept percentage change limits par based hai. Percentage change ki definition se shuru karo:

$\text{Percentage Change}=\frac{P_{\text{current}}-P_{\text{prev}}}{P_{\text{prev}}}\times 100$

$CF\%$ ki circuit limit ke liye, hum maximum allowable price find karna chahte hain:

$CF=\frac{P_{\text{upper}}-P_{\text{prev}}}{P_{\text{prev}}}\times 100$

$P_{\text{upper}}$ ke liye solve karo: $\frac{CF}{100}=\frac{P_{\text{upper}}-P_{\text{prev}}}{P_{\text{prev}}}$

$\frac{CF}{100}=\frac{P_{\text{upper}}}{P_{\text{prev}}}-1$

$P_{\text{upper}}=P_{\text{prev}}\times \left(1+\frac{CF}{100}\right)$

Similarly lower circuit ke liye: $P_{\text{lower}}=P_{\text{prev}}\times \left(1-\frac{CF}{100}\right)$

Step 1: Upper circuit calculate karo $P_{\text{upper}}=2500\times (1+0.20)=2500\times 1.20=₹3,000$

Ye step kyun? Hum maximum allowed price find karne ke liye 20% increase apply kar rahe hain.

Step 2: Lower circuit calculate karo $P_{\text{lower}}=2500\times (1-0.20)=2500\times 0.80=₹2,000$

Ye step kyun? Hum minimum allowed price find karne ke liye 20% decrease apply kar rahe hain.

Result: Reliance aaj ₹2,000 aur ₹3,000 ke beech trade kar sakta hai. Is band ke bahar ke orders reject ho jaate hain.

Step 1: Check karo ki opening circuit ke andar hai ya nahi

• Upper limit: $950\times 1.10=₹1,045$
• Lower limit: $950\times 0.90=₹855$
• ₹1,000 par opening limits ke andar hai ✓

Step 2: Stock tezi se 10:30 AM par ₹1,045 tak rise karta hai Ye kyun matter karta hai? Usne upper circuit reach kar liya — price aaj isse upar nahi ja sakti.

Step 3: Trading jaari rehti hai, lekin sirf ₹1,045 ya usse neeche Ye step kyun? Individual stocks ke liye, koi cooling-off halt nahi hota — ₹1,045 se upar ke buy orders simply reject ho jaate hain. ₹1,045 ya usse neeche sell karne wale sellers abhi bhi trade kar sakte hain.

Step 4: Index circuits se contrast karo Kyun? Sirf ek market-wide index circuit (jaise Nifty ±10% move karna) actual exchange-wide trading halt trigger karta hai cooling-off period ke liye.

Key Exceptions

Exception list:

1. Index derivatives (Nifty 50, Bank Nifty, Finnifty) – Koi circuit nahi
2. Stock futures aur options – Koi circuit nahi (lekin underlying stock mein price band hoti hai)
3. Currency aur commodity derivatives – Specific limits apply hoti hain

F&O Ban Period

MWPL Calculation

MWPL woh maximum combined open interest hai jo ek stock ke sabhi F&O contracts mein allowed hai.

Derivation:

MWPL ke do constraints hain — jo bhi lower hoga woh apply hoga:

Constraint 1: Free-float shares ka 20%

Ye prevent karta hai ki derivative positions actual tradeable stock supply ke relative bahut badi ho jaayein.

$N_{\text{max,shares}}=0.20\times N_{\text{free-float}}$

Jahan $N_{\text{free-float}}$ public trading ke liye available shares ki number hai (promoter holdings, strategic holdings, locked-in shares ko exclude karke).

Constraint 2: ₹500 crore notional value

$N_{\text{max,value}}=\frac{\text{₹}500\text{ crore}}{P_{\text{current}}}=\frac{5\times 10^9}{P_{\text{current}}}\text{ shares}$

Jahan:

• ₹500 crore $=500\times 10^7=5\times 10^9$ rupees
• $P_{\text{current}}$ rupees per share mein hai

₹500 crore cap kyun? Ye high-priced stocks mein excessive concentration ko prevent karta hai. Iske bina, ek high-priced stock mein reasonable share count ke saath bhi enormous notional exposure ho sakta tha.

Final MWPL: $\text{MWPL (shares)}=\min (N_{\text{max,shares}},N_{\text{max,value}})$

Ban trigger tab hota hai jab: $\text{Current Open Interest}>0.95\times \text{MWPL}$

Step 1: Free-float constraint ka 20% calculate karo $N_{\text{shares}}=0.20\times 350\text{ crore}=70\text{ crore shares}$

Ye step kyun? Ye available supply ke basis par maximum allowed hai.

Step 2: ₹500 crore notional constraint calculate karo $N_{\text{value}}=\frac{5\times 10^9}{3500}\approx 1.428\times 10^6\text{ shares}\approx 0.143\text{ crore shares}$

Ye step kyun? TCS jaise high-priced stocks rupee value se limit hote hain, share count se nahi.

Step 3: MWPL determine karo (minimum lo) $\text{MWPL}=\min (70\text{ crore},0.143\text{ crore})=0.143\text{ crore shares}$

Minimum kyun? Dono constraints satisfy hone chahiye; jo stricter hai woh bind karta hai.

Step 4: Ban threshold calculate karo $\text{Ban threshold}=0.95\times 0.143\text{ crore}\approx 0.136\text{ crore shares}$

Step 5: Check karo ki ban apply hota hai ya nahi Current OI = 0.5 crore shares > 0.136 crore shares → TCS F&O ban mein hoga

Ye kyun matter karta hai? Koi naye positions allowed nahi hain jab tak OI exit threshold se neeche nahi aa jaata.

Trader KYA KAR SAKTA hai:

1. Square off – Position close karne ke liye 100 futures becho ✓
2. Let expire – Expiry tak hold karo aur settle karo ✓
3. Exercise (agar options hain) – ITM options exercise karo ✓

Trader KYA NAHI KAR SAKTA:

1. ❌ Fresh long open karo – Additional futures kharido
2. ❌ Fresh short open karo – Naye futures becho
3. ❌ Increase karke rollover karo – Next month rollover karte waqt position increase nahi kar sakte
4. ✓ Same size rollover – 100 contracts ko next month rollover kar sakte ho (current square off + same size next month mein open = net zero fresh position)

Ye restrictions kyun? Goal overall open interest reduce karna hai, maintain karna nahi. Fresh positions allow karna purpose ko defeat kar deta.

Ban Removal Criteria

Stock ban se tab exit karta hai jab open interest MWPL ke 80% se neeche aa jaata hai. Ye ek buffer zone create karta hai:

• Ban enter karo: >95% MWPL
• Ban exit karo: <80% MWPL

15% gap (hysteresis) kyun? Flip-flopping rokta hai. Is buffer ke bina, stocks repeatedly ban mein enter aur exit karte jab OI 95% ke paas hover karta, jisse confusion aur operational issues hote.

Comparison: Circuit Filters vs F&O Ban

Common Mistakes

Ye sahi kyun lagta hai: Logical lagta hai ki agar spot trading limited hai, to derivatives bhi hone chahiye.

Fix: Stock derivatives mein koi circuit filters NAHI hote. Sirf underlying spot stock mein price bands hoti hain. Futures aur options tab bhi trade karte rehte hain jab spot stock apne band par hota hai, aur price discovery band se aage provide karte hain.

Example: Reliance spot upper band ₹3,000 par reach karta hai. Reliance futures ₹3,010, ₹3,020 par trade kar sakte hain, band se aage demand signal karte hue.

Ye sahi kyun lagta hai: Log individual-stock price bands ko market-wide index circuit breakers ke saath confuse karte hain, jo ACTUALLY trading halt karte hain.

Fix: Individual stocks ke liye, band hit karne ka matlab sirf ye hai ki limit se bahar orders reject ho jaate hain — band ke andar/par trading jaari rehti hai. Cooling-off trading halt sirf market-wide index circuits (Nifty/Sensex ±10%/15%/20%) par apply hota hai.

Ye sahi kyun lagta hai: "Ban" sunke lagta hai ki sab kuch block hai.

Fix: Tum ban ke dauran hamesha square off kar sakte ho. Ban sirf fresh positions ko prevent karta hai. Actually, exchange chahta hai ki tum exit karo taaki OI reduce ho. Ye ek capacity-full nightclub ki tarah hai — existing guests kabhi bhi ja sakte hain, lekin naye guests andar nahi aa sakte.

Ye sahi kyun lagta hai: Trigger condition mein "95%" hai, to log ise base calculation ke saath mix kar dete hain.

Fix:

• MWPL = Free-float ka 20% (total shares nahi) YA ₹500 crore limit (jo bhi lower ho)
• 95% woh MWPL ka threshold hai jo ban trigger karta hai
• Ye alag hain: $\text{Ban trigger}=0.95\times \text{MWPL}$

Practical Implications

Intraday Traders ke liye

1. Stock apne band par → Wrong side pe ho to exit karna mushkil (few counter-parties)
2. Solution: Hamesha stop-losses use karo jo circuit limits se tight hon
3. Derivatives advantage: Agar spot apne band par stuck ho to futures ke zariye exit kar sakte ho

F&O Traders ke liye

1. NSE ban list roz monitor karo (nseindia.com par publish hoti hai)
2. Rollover strategy: Agar stock expiry se pehle ban mein enter kare, tum rollover kar sakte ho (same size) lekin increase nahi kar sakte
3. Premium impact: Jab ban announce hota hai to options premiums spike kar sakte hain (implied volatility surge hoti hai)

Risk Management ke liye

1. 90% MWPL ke paas stocks se bacho → High ban risk
2. Band breaches → Extreme volatility signal karte hain (thesis reassess karo)

F&O ban alag hai. Imagine karo ki stadium mein limited seats hain (jaise ek movie theatre). Jab 95% seats ek hi team par betting karne walon se bhar jaayein, manager kehta hai "Ruko! Bahut saare log is ek team par betting kar rahe hain. Naye log betting tickets nahi khareed sakte, lekin jo andar hain woh kabhi bhi ja sakte hain." Ye dangerous overcrowding ko rokta hai.

Key difference: ek cap karta hai ki price kitna move kar sakti hai (circuit), doosra naye logon ko betting crowd mein join karne se rokta hai (F&O ban).

Ya: "Circuits Cap Price, Bans Block Size"

Connections

• 6.7.1-NSE-BSE-Market-Structure – Exchange architecture jo ye controls enable karti hai
• 6.7.5-Margin-Requirements-SPAN – High volatility ke dauran margins kaise adjust hoti hain
• 6.7.8-Market-Wide-Circuit-Breakers – Index-level trading halts (actual cooling-off mechanism)
• 5.4.3-Implied-Volatility-Calculation – Jab stocks F&O ban mein enter karte hain to IV spike hoti hai
• 3.2.7-Risk-Management-Position-Sizing – Portfolio risk ke liye MWPL monitor karna kyun zaroori hai
• 6.7.14-Settlement-Mechanisms – Ban period mein stuck positions kaise settle hoti hain

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