IPO Bidding Period Rules: Minimum Days, Extensions and Price Band Revisions

Most of us look at an IPO’s open and close dates, put them in the calendar and move on. But those dates aren’t picked freely. The IPO bidding period rules in SEBI’s Issue of Capital and Disclosure Requirements (ICDR) Regulations, 2018 decide how short a window can be, how long it can stretch, and what has to happen when a company changes its price band halfway through. Knowing them helps you read an extension notice correctly instead of guessing what it signals.

This piece walks through the rules as they stand in the ICDR Regulations as last amended on March 21, 2026, with a worked timeline using a made-up company. If you are newer to public issues, our guide to IPO investing in India covers the basics first.

The basic IPO bidding period rules: three to ten working days

Regulation 46(1) is short. An initial public offer must stay open for at least three working days and not more than ten working days, unless another part of the regulations says otherwise. That’s the whole frame. Everything else in this article is about moving around inside it.

Two words matter here. “Working days” means the count skips days on which bids are not taken. SEBI’s own FAQ on the ICDR rules notes that bids in a public issue are uploaded only on working days, even though the UPI system can create mandates on a holiday. So a Friday-to-Tuesday issue with a weekend in between is three working days, not five calendar days.

The second word is “initial”. The same three-to-ten structure is repeated for other public offers in the regulations. Regulation 142 covers further public offers by listed companies, Regulation 203 covers IPOs of Indian Depository Receipts, and Regulation 266 applies the same limits to public issues on the SME platform. The wording in each is nearly identical, which makes life simpler for anyone tracking issues across both boards.

Three working days is the floor and ten is the ceiling. Every extension, for any reason, has to fit under that ceiling.

What has to happen before bidding even opens

The bidding window sits at the end of a chain of deadlines, and a few of them are worth knowing because they explain why IPO calendars look the way they do.

• Validity of SEBI’s observations. Under Regulation 44(1), a public issue may be opened within twelve months from the date SEBI issues its observations on the draft offer document.
• Gap after filing the red herring prospectus. Regulation 44(2) says the issue can open only after at least three working days from the date the red herring prospectus (for a book built issue) or the prospectus (for a fixed price issue) is filed with the Registrar of Companies.
• Price band notice. Regulation 29(4) requires the floor price or price band to be announced at least two working days before the issue opens, in the pre-issue and price band advertisement. We covered what that advertisement contains in our explainer on the price band advertisement.

So when you see a band announced on a Monday for an issue opening Wednesday, that’s the two-working-day minimum at work, not a coincidence.

How wide a price band can be

Before getting to revisions, it helps to know the limits on the band itself. Regulation 29(2) says the cap of the band must be less than or equal to 120% of the floor price. A 2022 amendment added a lower limit: the cap must be at least 105% of the floor. Put simply, the top of the band has to sit somewhere between 5% and 20% above the bottom.

Take a hypothetical issuer, call it Kaveri Precision, with a floor of ₹380. Its cap can be anywhere from ₹399 (105% of 380) to ₹456 (120% of 380). A band of ₹380 to ₹400 works, since 400 divided by 380 is about 1.053, just over the 105% line. A band of ₹380 to ₹390 would not, because 390 is only about 102.6% of 380.

Regulation 29(3) adds one more check: neither the floor nor the final price can be below the face value of the shares.

Price band revisions: the three-working-day extension

This is the rule that catches people off guard. A company can revise its price band while bidding is on. Schedule XIII of the ICDR Regulations, which sets out the book building process, allows it with conditions:

• The maximum revision on either side cannot exceed 20%. The floor can move up or down by up to 20% of the floor disclosed in the red herring prospectus.
• The cap of the revised band still has to follow the 105% to 120% rule against the new floor.
• The revision has to be widely disseminated: the stock exchanges must be informed, a public notice issued, and the change shown on the relevant website and on the terminals of the syndicate members.
• If the band is lowered, the red herring prospectus or the public notice must say how any resulting shortfall in project financing will be met, and allotment cannot happen until that financing is tied up.

Then comes the time rule. Regulation 46(2) says that if the price band is revised, the issuer must extend the bidding period disclosed in the red herring prospectus by a minimum of three working days, still subject to the ten-working-day ceiling. Schedule XIII repeats the same point in its section on extension of the issue period.

The logic is fair to investors. A change in price changes the decision. Anyone who bid at the old band, or skipped the issue because of it, gets at least three more working days to look again.

A revised band is new information. The three extra working days exist so that investors can react to it, not so that the company can buy time.

A worked timeline with a revision

Let’s run Kaveri Precision through a full schedule. All dates and prices here are hypothetical.

The original plan. The red herring prospectus says bidding runs from Wednesday to Friday, three working days. The band is ₹380 to ₹400, announced the previous Monday, which meets the two-working-day notice.

The revision. On Thursday, with demand looking thin, the company cuts the band. It can move the floor down by at most 20% of ₹380, which is ₹76, so the lowest possible new floor is ₹304. It picks a smaller cut, a new floor of ₹342 (10% below ₹380) and a cap of ₹360. Check the width: 360 divided by 342 is about 1.053, so the cap is within the 105% to 120% range of the new floor.

The extension. The original close was Friday. Adding the minimum three working days, and assuming no market holidays, the new close lands on the following Wednesday (Monday, Tuesday, Wednesday). Total bidding days: Wednesday, Thursday and Friday of week one, plus Monday, Tuesday and Wednesday of week two. That’s six working days, comfortably under ten.

What changes for a bidder. Someone who bid at ₹400 in the first two days now sees a band of ₹342 to ₹360. A bid priced above the new cap is clearly stale. Retail individual investors also have the cut-off option, which SEBI’s FAQ notes is available only to them, and a cut-off bid follows whatever the final price is. Either way, the extra days are the window to review, modify or withdraw through the same intermediary. The FAQ is clear that the UPI app itself cannot change bid details; changes go through the intermediary, after which you get a fresh mandate request to approve, and modification requests can be acted on until 5:00 pm on the issue closing day.

Where the ten-day ceiling bites

Now imagine a different issuer that planned an eight-working-day window from the start. If it revises its band, the rules call for at least three extra working days, but the ten-day ceiling leaves only two. On a plain reading of Regulation 46, there is simply not enough room. That’s one practical reason issuers keep the original window shorter: a three-day issue leaves seven days of headroom for surprises.

Force majeure and other unforeseen events

Regulation 46(3) handles the other kind of extension. In case of force majeure, a banking strike or similar unforeseen circumstances, the issuer may extend the bidding period for a minimum of one working day, for reasons to be recorded in writing. Again, the ten-day ceiling applies.

Two details here changed in 2024. The word “unforeseen” was inserted, and the minimum extension was cut from three working days to one, through an amendment effective May 18, 2024. The price band revision rule was left at three working days. So the two kinds of extension now behave differently: a price change needs a longer reset, while a disruption like a bank strike can be covered by a shorter one.

When you see an extension notice, read the reason. A revision-driven extension tells you something about pricing. A force majeure extension usually tells you about plumbing, not demand.

A note on SEBI’s FAQ versus the regulation

If you read SEBI’s FAQ on the ICDR Regulations (updated as of May 15, 2025), you’ll find two slightly different descriptions. One answer says the price band can be revised and, if revised, the bidding period is extended by a further three days, with the total not exceeding ten working days. That matches the regulation. Another answer lists book built issues as open for three to seven working days, extendable by three days on a band revision.

The FAQ itself carries a disclaimer that it is not a legal document and points readers to the regulations for full particulars. The regulation text, Regulation 46(1), sets the limits at three and ten working days for an IPO. When the two read differently, go by the regulation.

Rules that run alongside the bidding window

A few other ICDR provisions apply while the issue is open, and they are useful to keep in mind.

• No hype on subscription. Regulation 43(4) bars any advertisement during the open period that gives the impression the issue is fully subscribed or oversubscribed, or that indicates investors’ response to it.
• Minimum application size. Regulation 47(2) says the minimum application size must fall in the range of a minimum application value of ₹10,000 to ₹15,000, measured with reference to the issue price.
• Minimum subscription. Under Regulation 45, the issue must receive at least 90% of the offer (with an exception for an offer for sale), or application money is refunded no later than four days from the issue’s closure. More on that in our piece on minimum subscription in an IPO.

How to read an extension as an investor

Here’s a short checklist we use when an issue gets extended.

1. Find the reason. The public notice will say whether it’s a band revision or an unforeseen event. They mean different things.
2. Compare old and new bands. A cut close to the 20% limit is a bigger statement than a small trim. Work out the percentage against the original floor yourself.
3. Look for the financing disclosure. If the band was lowered, the notice or red herring prospectus has to explain how any project funding shortfall will be met. Read that paragraph.
4. Recheck your bid. If you bid at a specific price, see where it sits against the new band. If you used cut-off, remember your blocked amount may change, and any change in amount comes as a fresh UPI mandate.
5. Note the new close date. Count working days, not calendar days, and keep the 5:00 pm modification deadline on the final day in mind.

None of this tells you whether an IPO is a good buy. It tells you whether the process is running the way the rules say it should, and it gives you the facts to make your own call with a clear head.

Disclaimer: This article is for educational purposes only and is not investment advice. The company, prices and dates in the examples are hypothetical. Regulations change; check the latest SEBI text and the offer documents, and consult a SEBI-registered adviser before investing.