How IPO Allotment Is Decided When an Issue Is Oversubscribed

An IPO is oversubscribed when the total number of shares applied for across all investor categories exceeds the number of shares on offer in that category. Oversubscription is measured separately for each investor category, not for the issue as a whole, because each category has its own reserved portion of the total issue and its own allotment rules.

The oversubscription figure is usually expressed as a multiple.

An issue that is oversubscribed 45 times in the retail category means the registrar received applications for 45 times the number of shares actually reserved for retail investors in that issue. A popular issue can easily see retail oversubscription in the double or triple digits while the qualified institutional buyer portion is oversubscribed by a much smaller multiple, because retail demand and institutional demand respond to different signals and are capped by different rules.

Term	What It Means	Why It Matters
Oversubscription ratio	Total shares applied for in a category divided by shares reserved for that category	Directly determines whether allotment is automatic or requires proportionate scaling or a lottery
Proportionate allotment	Shares allotted to each applicant in roughly the same ratio as their application size	Used for non institutional and qualified institutional categories when oversubscribed
Lottery allotment	A computerised random selection process used when full proportionate allotment is not possible for every applicant	Used for retail investors, where most applicants apply for the minimum lot size
Basis of allotment	The official document filed with the exchanges showing exactly how shares were allocated in each category	Public record that lets any applicant verify how the allotment process was actually run

SEBI requires every mainboard IPO to reserve fixed portions of the total issue for three broad categories of investors, and each category is allotted shares independently of the others.

Retail individual investors, those applying for shares worth up to Rs 2 lakh, are typically reserved at least 35 percent of the issue.

Non institutional investors, commonly called high net worth individuals or NIIs, who apply for amounts above Rs 2 lakh, are reserved at least 15 percent.

Qualified institutional buyers, the large institutional category that includes mutual funds and foreign portfolio investors, are reserved up to 50 percent.

Because these are separate pools, an issue can be wildly oversubscribed in the retail category while being only modestly oversubscribed among institutions, or the reverse.

Your allotment outcome depends entirely on the oversubscription level within your own category, not on the headline oversubscription number that gets reported in the news, which is usually a combined figure across all categories.

The headline oversubscription number you read in the news is a combined figure across three separate pools of shares. What actually determines whether you get an allotment is the oversubscription level inside your own investor category, which can be very different from the overall number.

When the retail category is not oversubscribed, or is oversubscribed by a small enough margin that every applicant can be given at least the minimum lot, allotment is straightforward and proportionate. Every applicant receives at least one lot, and any leftover shares are distributed in additional full lots based on the size of each application.

The more common scenario for popular issues is that the retail category is oversubscribed to the point where there are simply not enough shares for every applicant to receive even the minimum lot. SEBI's rules require that in this situation, allotment must be done through a computerised lottery system rather than splitting shares into fractions.

A registrar cannot allot half a lot to twice as many people, so instead the system randomly selects which applicants receive a full minimum lot and which receive nothing.

This is the single most important fact for retail investors to understand: once retail oversubscription crosses the point where every applicant cannot receive at least one lot, the outcome becomes a matter of random chance, not the size of your application, how early you applied, or which broker you used.

Retail Oversubscription Level	How Allotment Works	Effect on the Applicant
Not oversubscribed or undersubscribed	Every applicant gets full shares applied for	Guaranteed allotment in line with the application
Mildly oversubscribed	Every applicant gets at least the minimum lot; extra shares split proportionately	Most applicants receive shares, sometimes fewer than applied for
Heavily oversubscribed	Computerised lottery decides which applicants get one minimum lot; others get none	Allotment becomes random; application size beyond one lot does not help

The lottery is conducted by the registrar to the issue, typically a SEBI registered entity such as Link Intime or KFin Technologies, using a system that SEBI has approved for fairness and auditability. Every valid retail application of one lot is treated as a single lottery ticket, regardless of whether the applicant applied for one lot or the maximum permitted number of lots within the retail limit.

This is a detail many applicants miss. If the retail portion can only satisfy, say, one in five applicants, the registrar effectively runs a random draw where each lot sized application has roughly a one in five chance of being picked, and an applicant who applied for three lots simply gets three separate chances in the same draw rather than an improved chance per lot.

Applying for the maximum number of lots in the retail category increases your total number of draws in the lottery and therefore your odds of getting at least one lot, but it does not guarantee a better outcome the way proportionate allotment would in the NII or QIB categories.

The full basis of allotment, including the exact number of valid applications received, the number of applicants who received shares, and the lottery methodology, is filed with the stock exchanges and published publicly. Investors who want to verify that the process was run fairly for a specific issue can find this document on the BSE or NSE website under the relevant IPO listing.

Non institutional investors and qualified institutional buyers are not allotted shares through a lottery. Both categories use proportionate allotment, where every applicant receives shares in roughly the same ratio as the rest of their category, scaled down to fit the available shares.

If the non institutional category is oversubscribed 20 times, an applicant who applied for shares worth Rs 10 lakh would receive approximately one twentieth of that application, subject to rounding and minimum allotment rules set by the registrar. This means larger applications in these categories do translate into proportionally larger allotments, unlike the retail lottery where application size beyond the maximum retail limit has no further effect.

In the retail category, a bigger application buys you more tickets in a lottery. In the non institutional and institutional categories, a bigger application buys you a proportionally bigger slice of a fixed allocation. These are fundamentally different mechanisms, and conflating them is the most common source of confusion about IPO allotment.

What Genuinely Affects Your Odds

• Applying through a single demat account rather than multiple applications under the same PAN: SEBI rules prohibit an individual from submitting more than one application using the same PAN in a given IPO, and registrars actively reject duplicate or technically invalid applications before the lottery is even run.

• Applying for the maximum permitted lots within the retail limit rather than a single lot: this increases the number of draws you get in the lottery, which modestly improves your probability of receiving at least one lot, though it does not guarantee an outcome.

• Applying through family members with separate PAN and demat accounts: this is legal and commonly used, since each family member with their own valid account and PAN is treated as an independent applicant with an independent chance in the lottery.

• Ensuring the application is technically valid and fully funded through ASBA at the time of bidding: applications that are rejected for technical reasons, such as insufficient blocked funds or incorrect details, are removed from the pool before the lottery runs and do not get a chance regardless of intent.

• Avoiding cut off price bidding errors: applying at a price below the eventual cut off price, where permitted, can result in technical rejection in some structures, so applicants are generally advised to bid at the cut off price for the highest probability of remaining a valid applicant.

Small and medium enterprise IPOs, listed on the separate SME platforms of BSE and NSE, follow the same broad category structure but with different minimum allottee requirements given the smaller overall issue sizes. SEBI requires that an SME issue have a minimum number of allottees, and because lot sizes in SME IPOs are typically much larger in value than mainboard lots, the lottery dynamics can look different even when the headline oversubscription number appears similar to a mainboard issue.

Investors applying to SME IPOs should treat the oversubscription multiple with some caution and check the specific lot size and minimum application value before assuming the odds resemble a typical mainboard retail lottery.

Disclaimer: This article is for educational purposes only and does not constitute investment advice. The description of SEBI's IPO allotment framework, including reservation percentages, the retail lottery process, and proportionate allotment rules, reflects the regulations as understood in June 2026 and is subject to amendment by SEBI. Actual allotment outcomes depend on the specific terms of each issue as disclosed in its prospectus and basis of allotment. Readers should consult the official basis of allotment for any issue they applied to and seek a qualified financial adviser before making investment decisions.