Think about the last time you used a key to open a lock. You don't see what happens inside. You just insert the key, turn it, and either the door opens or it doesn't. Behind that simple action sits a small mechanism of pins and springs, quietly deciding, in a fraction of a second, whether your key matches what the lock is built to accept.
Applying for an IPO works almost exactly like this. You submit your application, the screen says "applied," and then, for a few days, nothing visible happens. But behind that silence, a mechanism is running, verifying your application, sorting it against thousands of others, and eventually deciding whether your key, your application, gets you through the door. Let's open that mechanism and look at exactly what's happening inside.
THE KEY GOES IN: YOUR APPLICATION GETS LOCKED
When you apply for an IPO, your bid amount doesn't leave your bank account. It gets blocked, through ASBA or UPI, sitting untouched in your own account like a key held steady in a lock, neither accepted nor rejected yet. This is an important detail many first-time applicants miss: nothing is debited at this stage. If your application is ultimately unsuccessful, there's no "refund" in the traditional sense, because your money never actually left in the first place.
This blocked amount is your place in line, proof that you're a genuine, funded applicant, not a placeholder bid with nothing behind it.
THE ISSUE CLOSES: THE LOCK STARTS READING THE KEY
Once the IPO's subscription window closes, on what's called the "T" day, the real mechanism begins. Just as a lock reads every ridge and notch on a key before deciding whether it fits, the registrar to the issue, a SEBI-registered institution appointed specifically for this job, starts reading every single application that came in.
This is where applications get sorted by category: Retail Individual Investors, Non-Institutional Investors, and Qualified Institutional Buyers. Each category is like a different chamber inside the same lock, with its own set of pins that need to align before that chamber opens.
T+1: THE PINS START FALLING INTO PLACE
On the very next working day after closing, by 6 PM, the registrar finalises what's called the Basis of Allotment, working in consultation with the stock exchange to make sure everything checks out. This is the moment the lock's pins either align or they don't.
Here's where the mechanism becomes genuinely interesting, and where most applicants misunderstand how it works. If the IPO is undersubscribed, meaning fewer applications came in than shares available, every single valid applicant gets their shares. The key simply fits, no resistance at all.
But if the issue is oversubscribed, which is far more common for popular IPOs, the retail category moves to a computerised lottery. And here's the detail that surprises most people: every valid retail application, regardless of how many lots you bid for, becomes exactly one entry into that lottery. Applying for five lots doesn't give you five keys to try. It gives you one key, same as everyone else, with the lottery deciding whether that one key turn.
For the NII and QIB categories, the mechanism works differently, more like a proportionate dial than an all-or-nothing switch. If the NII segment is oversubscribed eight times over, someone who applied for Rs. 8 lakh worth of shares typically ends up allotted around Rs. 1 lakh worth, scaled down in exact proportion to how oversubscribed that category was.
T+2: THE LOCK RELEASES WHAT IT DIDN'T KEEP
The day after the Basis of Allotment is published, the mechanism does something quietly important: it releases whatever it didn't keep. If your application wasn't successful in the lottery or the proportionate allotment, the amount that was blocked in your account gets unblocked, UPI applicants and ASBA applicants on the same timeline. Nothing was ever taken from you, so there's technically nothing being "returned," but you'll see the block lifted and the funds genuinely usable again.
This is also the point where successful applicants see their allotted shares get ready for credit, the lock mechanism now preparing to open the door.
T+3: THE DOOR OPENS
On the third working day after the IPO closes, two things happen almost simultaneously. Your allotted shares get credited directly into your demat account, and the company's stock begins trading on the exchange. This is SEBI's mandatory T+3 listing timeline, in effect since December 2023, which compressed what used to be a much longer wait into just three working days from the moment bidding closed.
If you were allotted shares, you can now see them sitting in your demat account, free to hold or sell as you choose. If you weren't, your funds have already been released a day earlier, sitting exactly where they were before you applied, none the worse for the attempt.
WHY UNDERSTANDING THIS MECHANISM ACTUALLY MATTERS
Knowing how the lock works doesn't change whether your key turns, the lottery is still genuinely random for oversubscribed retail allotments. But understanding the mechanism changes how you experience the process. You'll know that applying for more lots in retail doesn't improve your odds the way many assume it does. You'll know that silence between T and T+1 doesn't mean anything went wrong, it's simply the registrar doing its verification work. And you'll know exactly when to check your allotment status, rather than refreshing your phone anxiously every hour from day one.
It also reframes what "winning" an IPO actually means. A successful allotment isn't a guarantee of listing gains, it's simply confirmation that your key fit the lock this time. What happens to the stock's price after listing is an entirely separate mechanism, shaped by market demand, company fundamentals and broader sentiment, not by the allotment lottery that got you there.
THE HONEST TAKEAWAY
There's a reassuring symmetry to this entire process once you see it clearly. Your money is never at risk while it's blocked, waiting to see if the key fits. If it doesn't, you lose nothing but a little anticipation. If it does, shares land in your account within three working days of the issue closing, fully transparent, fully regulated, with no broker able to influence who the lottery favours.
The next time you apply for an IPO, you'll know exactly what's happening behind that quiet screen that just says "applied": a registrar reading every key, a lottery deciding the ones that are tied, and a mechanism built, by regulation, to be fair to every applicant holding one.
Whenever you're ready to apply for your next IPO, the GoPocket mobile app lets you track your application right through to allotment and listing, so you're never left wondering what's happening behind the screen.
