IPO Allotment Probability vs Actual Allotment
Overview
Many investors use IPO allotment probability calculators to estimate their chances of receiving shares. However, there is often confusion between probability and actual allotment. These two concepts are related but fundamentally different.
This article explains how IPO allotment probability works, how actual allotment happens, and why the two should never be treated as the same.
What Is IPO Allotment Probability?
IPO allotment probability is a statistical estimate.
It is calculated using:
- Number of available shares or lots
- Subscription levels in a category (RII, NII, QIB, etc.)
- Number of valid applications
- Assumptions based on SEBI-prescribed allotment methods
Probability answers only one question:
“Based on current demand and supply, how likely is an application to get selected?”
It does not decide who gets shares.
What Is Actual IPO Allotment?
Actual IPO allotment is the final allocation of shares done after the IPO closes.
It is carried out by:
- The IPO registrar
- Using verified subscription data
- Following SEBI ICDR Regulations
- Through computerized allotment logic
Actual allotment determines:
- Who receives shares
- How many shares are allotted
- Who receives refunds
Once finalized, actual allotment overrides all estimates.
Key Difference Between Probability and Actual Allotment
IPO allotment probability:
- Is an estimate
- Is theoretical
- Can change during the IPO period
- Depends on assumptions
- Helps in understanding odds
Actual allotment:
- Is final
- Is rule-based
- Is registrar-controlled
- Uses verified data
- Cannot be influenced by probability
Probability explains likelihood, not outcome.
Why Probability Can Never Match Actual Results Exactly
Even with accurate data, probability:
- Cannot account for invalid or rejected applications
- Cannot predict final cut-off bidding behavior
- Cannot foresee last-day subscription spikes
- Cannot influence random lottery selection
For example, a 20% probability:
- Does not mean 1 in every 5 applicants will surely get shares
- Means each applicant has an independent 20% chance
An applicant can still receive:
- No allotment at 80% probability
- Allotment at 5% probability
Role of Randomness in Actual Allotment
In oversubscribed categories:
- All valid applications enter a lottery
- The system randomly selects applications
- Each application has an equal chance
Probability does not affect this randomness.
The lottery:
- Does not consider application size (in retail)
- Does not consider past allotments
- Does not consider probability estimates
Live IPO vs Final Allotment
During live IPOs:
- Subscription numbers keep changing
- Probability estimates fluctuate
- Demand patterns evolve daily
After IPO closure:
- Data is frozen
- Invalid applications are removed
- Final allotment logic is executed
This is why probabilities shown during live IPOs are temporary and non-final.
Common Misunderstanding Among Investors
A frequent mistake is assuming:
- Higher probability means guaranteed allotment
- Lower probability means no chance
In reality:
- Probability only describes odds
- Actual allotment is a single yes/no outcome
- Even low-probability events happen regularly
How Probability Tools Should Be Used
Probability tools should be used to:
- Understand demand–supply imbalance
- Compare IPO popularity across categories
- Set realistic expectations
- Learn how oversubscription impacts chances
They should not be used to:
- Decide whether allotment will happen
- Assume assured outcomes
- Replace independent judgment
Final Conclusion
IPO allotment probability and actual allotment serve very different purposes.
Probability explains how likely selection may be, while actual allotment decides who actually gets shares.
Actual allotment is always final, binding, and independent of any probability estimate.