Book Building Process in an IPO: How Bids Inside the Price Band Set the Final Price

Most of us first meet the book building process as a line on an IPO poster: “Price band ₹X to ₹Y.” We pick a lot, tick a box and wait for the allotment SMS. But that price band is only the start of the story. The final issue price is set after the bidding closes, and it comes out of thousands of bids sitting in a book that anyone can watch fill up in real time. If you understand how that book is built, you read subscription numbers, cut-off bids and listing-day moves very differently.

This guide walks through what book building is, how the rules work in India, who gets what share of the issue, and a full worked example with a made-up company so you can see the arithmetic.

What the book building process actually is

SEBI’s own investor FAQ on public issues describes book building as “a process of price discovery”. The issuer discloses a price band or floor price before the issue opens. Investors then bid, saying how many shares they want and at what price. On the basis of the demand received at the various price levels inside the band, the book running lead manager (the merchant banker running the issue) works with the company to arrive at the price at which the shares are issued.

So the price isn’t fixed on day one. It’s discovered. That’s the whole point.

The global version works on the same idea. Investopedia’s explainer on book building describes underwriters inviting bids from large investors and fund managers, building a “book” of that demand and using it to set the final price before shares are allocated to accepted bidders. It also makes a point we should keep in mind: the price suggested by the book does not guarantee that demand will hold up once the stock starts trading.

Fixed price vs book built issues

An Indian public issue is priced in one of two ways. In a fixed price issue, the company decides the price upfront and prints it in the offer document. In a book built issue, the price is discovered from the demand that comes in at different price levels, according to the SEBI FAQ.

Which route a company takes isn’t always a free choice. The FAQ says that if a company doesn’t meet the eligibility conditions in regulation 6(1) of the SEBI ICDR Regulations, 2018 (the profitability-type entry norms), it must compulsorily use the book built route. That second route, often called the QIB route, comes with a much heavier institutional allocation, which we cover below.

The FAQ also notes that a price band is something you find in the red herring prospectus of a book built issue. So any IPO that comes with a floor and a cap is a book built one, which is why understanding the book matters more than memorising the fixed price rules.

The rules that shape the book

A handful of SEBI rules decide how the book looks before a single bid arrives. All of these come from the SEBI investor FAQ linked above.

• Price band width. The gap between the floor and the cap must be at least 5% and at most 20%. We’ve broken this down in more detail in our post on the price band in an IPO.
• When the band is announced. For an IPO, the floor price or price band has to be announced at least two working days before the issue opens.
• How long the book stays open. A book built public issue stays open for 3 to 7 working days. If the price band is revised, bidding is extended by three days, but the total bidding period can’t go beyond ten working days.
• Who counts as retail. A retail individual investor is someone bidding for not more than ₹2,00,000 worth of shares.
• Open book. India uses an open book system. Bid data is put up on the BSE and NSE websites on a consolidated basis while the issue is live, so investors can see demand building.

That last rule is easy to skip past, yet it’s the reason “Day 2 subscription status” headlines exist. In a closed book system, which the FAQ also describes, bidders have to decide on a price without seeing what anyone else has bid. In India, you can watch the book fill before you commit.

The price band tells you where the bidding can happen. The book tells you where the money actually is.

Who gets which slice of the issue

A book built issue isn’t one big pool. The net offer to the public is split into investor categories, and each category gets its own share of the book. The SEBI FAQ sets out two templates.

Voluntary book building under the profitability route:

• Not less than 35% of the net offer for retail individual investors.
• Not less than 15% for non-institutional investors (NIIs), meaning anyone who is neither retail nor a qualified institutional buyer.
• Not more than 50% for qualified institutional buyers (QIBs).

Compulsory book building (the QIB route):

• At least 75% of the net offer must be allotted to QIBs, and if that isn’t achieved, the full subscription money is refunded.
• Not more than 15% for NIIs.
• Not more than 10% for retail individual investors.

The difference is worth sitting with. In a QIB-route issue, retail gets at most a tenth of the net offer, and the deal lives or dies on institutional demand. When you see an IPO with a tiny retail portion, that’s usually your cue to read which entry route the company used.

QIBs, by the way, are a defined list in the FAQ: mutual funds, foreign portfolio investors (other than individuals, corporate bodies and family offices), scheduled commercial banks, insurance companies, and provident and pension funds with a minimum corpus of ₹25 crore, among others.

A worked example: building the book for a made-up issue

Let’s build one. Every number in this section is hypothetical, chosen only to show how the mechanics work.

Say Kaveri Components Ltd (not a real company) comes to market under the profitability route with a net offer of 1 crore shares. The price band is ₹190 to ₹200. The spread is ₹10 on a floor of ₹190, or about 5.3%, which sits inside SEBI’s 5% to 20% window. The lot size is 75 shares.

Step 1: split the offer. Using the minimums and maximums above, the issue reserves 35 lakh shares for retail (35%), 15 lakh for NIIs (15%) and 50 lakh for QIBs (50%).

Step 2: work out the retail ceiling. One lot at the cap price costs 75 × ₹200 = ₹15,000. Thirteen lots cost ₹1,95,000, which is under the ₹2 lakh retail limit. Fourteen lots would cost ₹2,10,000, which tips the bid into the NII category. So the most a retail investor can bid for is 13 lots, or 975 shares.

Step 3: watch the book. Suppose that by the close, bids across all categories look like this, counting each price level and everything bid above it:

Demand at the cap alone covers the issue 1.6 times. In a book like this, the lead manager and the company have every reason to price at ₹200. Bids at lower prices simply don’t make it.

Step 4: run the weaker version. Now imagine a softer book where only 60 lakh shares are bid at ₹200, and the cumulative figure crosses 1 crore only at ₹195 (say 1.05 crore). The issue might then be priced at ₹195. What happens to our investors?

• A retail investor who bid at ₹198 is fine. Their bid is above the discovered price, so it stays valid, and the shares are allotted at the final issue price.
• A retail investor who bid at ₹192 is out. The SEBI FAQ is clear that a price bid below the discovered price can become invalid.
• A retail investor who ticked cut-off is safe. Cut-off bids always remain valid for allotment, whatever price is discovered within the band.

Step 5: allot the retail portion. Back to the strong book. Suppose retail bids come to 1.05 crore shares against 35 lakh on offer, so retail is subscribed 3 times. There are 35,00,000 ÷ 75 = 46,666 full lots available (the leftover 50 shares don’t make a full lot). If 1.4 lakh retail investors applied, there are three applicants for every lot. SEBI’s rule is that each retail investor should get at least the minimum bid lot, but only subject to the shares available, and the rest is allotted proportionately. With three applicants per lot, most people get nothing. Our post on the IPO basis of allotment explains how the registrar decides who gets the lots in that situation.

Bidding 13 lots in an oversubscribed issue rarely gets you 13 lots. It usually gets you one, or none.

That’s the quiet lesson of the example. Retail investors often bid the maximum because the book looks hot, but in a heavily oversubscribed retail portion, the size of your bid barely changes your odds.

Cut-off bids: why most retail money uses them

The cut-off option, per the SEBI FAQ, is available only to retail individual investors bidding up to ₹2,00,000. Ticking it means you’re willing to buy at whatever price is discovered within the band. The trade-off is simple. You give up the ability to name a lower price, and in return your bid can’t be knocked out by the price discovery itself.

For most retail investors, that’s the right trade. You’re rarely going to win a pricing argument against the institutions setting the book. We’ve written a separate piece on how retail bids at the IPO cut-off price work.

One more retail detail from the FAQ: you can revise the quantity or price of your bid, but the revision has to be done before the issue closes. You can also cancel your bid any time until the closing date by approaching the registrar.

Reading the book while the issue is open

Because the book is open, we get to see it fill. A few habits help.

Look at categories, not the headline. A “5x subscribed” headline can hide a book where QIBs are 15x and retail is barely 1x, or the other way round. The categories tell you who believes in the price.

Don’t judge on Day 1. The book is only final when bidding closes. A sleepy first day doesn’t automatically mean a weak book, and a strong first day driven only by retail doesn’t mean the institutions agree.

Watch for a band revision. If the company revises the price band, the bidding period gets three more days, capped at ten working days in total. A revision mid-issue is a signal in itself, and it’s worth asking why the original band didn’t hold.

Remember what the book is. It’s demand at a point in time, inside a band the company and its bankers chose. Investopedia’s point stands: a good book doesn’t guarantee that the same demand shows up on listing day.

What book building doesn’t tell you

A full book tells you plenty of people want the shares at this price. It doesn’t tell you the price is cheap. SEBI’s FAQ is explicit that it plays no role in fixing the price. The issuer and the merchant banker decide it based on market demand, and the offer document discloses the parameters behind it, such as EPS, P/E, return on net worth and peer comparisons.

That’s the section we’d read before bidding, not after. A book can be oversubscribed because the business is good, because the market is in a generous mood, or because everyone is chasing listing gains. The subscription number can’t tell you which one it is. The valuation section of the red herring prospectus at least gives you a fair shot.

It’s also worth remembering that, according to the same FAQ, a company can’t allot any shares in a public issue unless there are at least 1,000 prospective allottees. That rule rarely bites on a big mainboard issue, but it’s a reminder that the process has minimum thresholds built into it.

A short checklist before you bid

• Check the price band and work out the spread between the floor and the cap.
• Find out whether the issue uses the profitability route or the QIB route, because that decides how big the retail portion is.
• Work out your maximum retail bid: the number of lots at the cap price that stays within ₹2 lakh.
• Decide whether to bid at cut-off. For most retail investors, it removes the risk of being priced out.
• Track category-wise subscription on the exchange website, especially on the last day.
• Read the basis for issue price section before you decide the price is fair.
• Assume you may get one lot or none if retail demand is several times the shares on offer.

For the bigger picture on applying, allotment and listing, our guide to IPO investing in India pulls the pieces together. Once you’ve seen a book built from the inside, even on paper, the next IPO headline stops being a number and starts being a story about who is buying, at what price, and why.

Disclaimer: This article is for information and education only and is not investment advice. The worked example uses a hypothetical company, price band and bid figures. Rules are as described in the linked SEBI and Investopedia sources at the time of writing. Please consult a SEBI-registered investment adviser before making any investment decision.