How the Computerized IPO Lottery Algorithm Works

When an Indian IPO is oversubscribed in the Retail or Non-Institutional Investor (NII) categories, the designated stock exchange and registrar (Link Intime, KFintech, Bigshare) execute an automated Computerized Draw of Lots (Basis of Allotment).

Many investors mistakenly believe that applying for maximum lots or applying early on Day 1 increases lottery odds. This guide explains the exact mathematical algorithm mandated by SEBI.

1. The Core Principle: "One Application = One Lottery Ticket"

Under SEBI guidelines established in 2012:

In the Retail Individual Investor (RII) category, all valid applications are treated equally as single-lot lottery entries, regardless of whether the applicant bid for 1 lot (₹14,000) or 13 lots (₹1,95,000).

If Retail is oversubscribed, the registrar does not divide shares proportionately; instead, it executes a computerized random draw to allocate exactly one minimum market lot to lucky winners until the entire retail quota is exhausted.

2. The Step-by-Step Registrar Lottery Algorithm

```

Step 1: Technical Rejections Eliminated (Duplicate PAN, UPI Failures, Below Cut-off)

Step 2: Total Valid Applications Counted (N)

Step 3: Total Available Minimum Lots Calculated (L)

Step 4: Oversubscription Ratio Determined (R = N / L)

Step 5: Pseudo-Random Number Generator (PRNG) Seeds Lottery Draw

Step 6: Exactly L Winners Selected & Allotted 1 Lot Each

```

Mathematical Example:

Retail Shares Reserved: 10,00,000 shares

Lot Size: 50 shares

Total Available Retail Lots ($L$): $rac{10,00,000}{50} = \mathbf{20,000 ext{ Lots}}$

Total Valid Retail Applications Received ($N$): 1,60,000 applications

Oversubscription Ratio ($R$): $rac{1,60,000}{20,000} = \mathbf{8x}$

Individual Allotment Odds: $1 ext{ in } 8 = \mathbf{12.5\%}$ per PAN application.

3. How to Legally Multiply Your Lottery Odds

Since bidding multiple lots on one PAN does not improve odds, the only mathematically valid way to increase your winning probability is submitting 1 minimum lot across separate unique PAN accounts within your family:

1 Family Demat: $12.5\%$ probability

4 Family Demats: $1 - (1 - 0.125)^4 = \mathbf{41.4\%}$ probability of winning at least 1 lot!

Learn all 7 rules in our [Family Demat Optimization Guide](/blog/maximize-ipo-allotment-odds-family-accounts) and check results on our [IPO Allotment Status Checker](/allotment).

*Disclaimer: This analysis is for educational purposes only.*

How the Computerized IPO Lottery Algorithm Works: Step-by-Step Selection Math for Retail & sNII

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