It is the first number most Indian investors look up before an IPO and the only one nobody is accountable for. Grey market premium, or GMP, is the amount above the issue price that buyers will pay for shares in an unofficial market before listing, and with India heading into a heavy IPO window it is being quoted everywhere.
It measures something real. It just does not measure what most people think it does.
What the number is actually made of
The mechanics are simpler than the mystique.
Before an IPO lists, a small circle of traders buys and sells the right to shares that do not yet exist on an exchange, settling on trust rather than through a clearing corporation. The premium they pay over the issue price becomes the quoted GMP. There is no order book you can inspect, no published volume, and no obligation on anyone to honour a quote.
That is why the number can be both genuinely informative and completely unreliable in the same week. It reflects what a small number of people believe about demand today, which is real information, but it carries none of the safeguards that make an exchange price trustworthy.
Where GMP misleads
Three specific failure modes, all of which show up in most IPO cycles.
Thin volume moves it easily. A market with few participants can be moved by a small number of trades, deliberately or otherwise, so the premium is more sensitive to activity than to information.
It measures the wrong demand. Retail enthusiasm and institutional conviction are different things. Subscription data during the issue window, especially the qualified institutional buyer portion, is real disclosed money committing to a price, while GMP is chatter about what someone might pay.
It is a snapshot, not a forecast. The premium quoted the day a price band is announced routinely bears little resemblance to the one on listing day, because the intervening period includes the actual subscription numbers and the broader market's mood.
What to read instead
The prospectus is dull and it is the only document with accountability behind it.
Start with whether the issue is a fresh issue or an offer for sale, because that determines whether your money funds the company's growth or an existing shareholder's exit. A pure offer for sale is not automatically bad, but it means the business receives nothing, a distinction that matters in the current NSE listing, covered in our NSE IPO analysis.
Then the valuation. Compare the price band against the company's recent earnings and against listed peers, which is the arithmetic that decides long-run returns regardless of what happens on listing day. Our NSE vs BSE comparison shows what that exercise looks like in practice, and the mechanics of applying are in our how to apply for an IPO in India guide.
Finally, subscription figures as they come in. Those are disclosed, verified and regulated, which is three things GMP is not.
The uncomfortable logic of listing gains
Grey market premiums are highest when enthusiasm is highest, and enthusiasm is highest when issues are priced most fully. That is not a coincidence, it is how book building works: bankers price into demand, so strong demand generally means a fuller price rather than a bargain.
There is also an allotment reality that makes GMP-chasing self-defeating for most retail investors. In an oversubscribed retail portion, allotment is decided by lottery, so the investor who applied because of a high premium has no better chance of receiving shares than anyone else, and no ability to size the position.
Risks to monitor
The second risk is anchoring. A premium quoted early sets an expectation that colours how the actual price band is received, even when the two are unrelated.
The third is that listing-day pops and long-run returns are different questions. A stock can open sharply higher and still be a poor investment, or open flat and compound for years. GMP speaks only to the first day. This is general information, not investment advice.
The honest way to use GMP is as weather, not as a compass. It tells you the mood in a small room, on one day, with no obligation attached, and the prospectus tells you what you would actually own.