IDX Trades Are Supposed to Settle in Two Days. Here's What Happens When One Side Can't Deliver
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6 min read
On 28 September 2026, the Indonesia Stock Exchange (IDX) is set to publish something it has not published in over a year: an actual list of stocks investors can short sell again. Early reporting says the first list will hold only three to five names, pulled from the LQ45 group of Indonesia's most actively traded stocks, not the full 45. That is a strikingly short list for a stock exchange with hundreds of listed companies.
The reason comes down to a two-day clock that runs on every single IDX trade, whether it involves short selling or not. Every trade you place has to settle, meaning shares and cash actually change hands, within two exchange days. Almost every time, that happens without a hitch. This article is about the small number of times it does not, what IDX and its clearing house do about it, and why that risk is exactly what keeps the new short-selling list so short.
IDX runs on a T+2 settlement cycle: "T" is your trade date, and the "+2" counts two exchange days after it, not calendar days. By T+2, the seller's shares are supposed to move out of their account and the buyer's cash is supposed to move in, cleared through PT Kliring Penjaminan Efek Indonesia (KPEI, the clearing house) and recorded by PT Kustodian Sentral Efek Indonesia (KSEI, the central depository). Our companion piece on the T+2 settlement cycle covers how this works when everything goes right.
A settlement failure, called gagal serah (literally "failed to hand over") in Indonesian market language, is what IDX calls it when a seller's broker cannot actually deliver the shares on time. The seller might not have owned enough of the stock to begin with, a court or regulator might have frozen the shares before delivery, or a chain of intermediary transactions might simply not clear in time. Whatever the cause, the buyer who paid for those shares still needs to receive something.
Under Peraturan Bursa Nomor II-A, the exchange rule governing equity trading, a broker who cannot deliver has two paths.
The first is a buy-in: the broker goes into the Cash Market and buys the same stock from someone else who does have it, then hands those shares to the original buyer instead. This keeps the buyer's position exactly what they expected, just from a different seller.
The second is Alternate Cash Settlement (ACS), used when a buy-in is not possible or the broker chooses not to attempt one. Instead of shares, the failing broker pays cash, and the amount is set punitively on purpose: 125% of the highest price that stock traded at, across the relevant Regular and Cash Market sessions around the settlement date. If a stock traded as high as Rp1,000 in the relevant window, the broker owes Rp1,250 per share, not Rp1,000, regardless of what the original trade was actually priced at.
ACS owed = Shares undelivered × Highest price in the settlement window × 125%
This is not a theoretical rule. Two well-documented cases show how it plays out.
In December 2017, KSEI froze PT Media Nusantara Citra Tbk (MNCN) shares held by PT Global Mediacom Tbk over a suspected embezzlement case. A broker who had already sold roughly 11 million MNCN shares on 12 December 2017 could no longer deliver them, since the underlying shares were locked. The broker settled the shortfall with ACS, paying out Rp16 billion, per Bareksa's reporting at the time, corroborated by Kontan and Antara News coverage of the same KSEI freeze.
A year later, a similar freeze hit PT Transcoal Pacific Tbk (TCPI), this time from a police blocking order on shares held at KSEI. The disruption was large enough to move the whole market's numbers: KPEI's industry-wide ACS total for 2018 came to Rp85.96 billion, a 90% jump from Rp45.22 billion in 2017, almost entirely attributed to the TCPI case, per Bisnis.com's year-end report, with the same figure independently confirmed by Neraca.co.id and CNBC Indonesia.
Two years after that, ACS activity spiked again on its own: KPEI recorded Rp82.99 billion in ACS for 2020, up 99.87% from Rp41.52 billion in 2019, per a separate Bisnis.com report. Neither the MNCN nor the TCPI case involved short selling specifically; both came from shares being frozen for unrelated legal reasons. They matter here because they show the buy-in and ACS machinery actually running, at real rupiah cost, not just sitting in a rulebook.
Short selling adds a second way a delivery can fail. A short seller sells shares they do not own, borrowed for the trade, and is on the hook to return equivalent shares later. If the stock is illiquid, meaning few shares change hands on a normal day, the short seller can struggle to source shares to return, turning an ordinary short trade into exactly the kind of failed delivery described above, at the buyer's expense.
That is the logic behind how IDX is screening its restarted short-selling programme, reactivated in phases starting 15 September 2026 after two earlier delays ordered by Indonesia's Financial Services Authority (OJK), in September 2025 and March 2026, per Kontan's and Katadata's coverage of the relaunch. The eligible-stock list, due 28 September 2026 under IDX announcement Peng-00168/BEI.POP/09-2026 and effective for October 2026 trading, is drawn from LQ45 but will not include the full 45, and stocks priced at Rp50 or below are excluded outright, precisely because thin, low-priced stocks are the ones most likely to produce a failed delivery. As of this writing, IDX has not published which specific three to five stocks made the first cut, and this article makes no claim about which names will be on it.
This restriction is separate from the T+4 forced-sell rule that applies to margin trading specifically; our explainer on IDX margin trading and forced-sell rules covers that different mechanism.
For an ordinary buy-and-hold investor, a settlement failure on your own trade is rare and, when it happens, is the broker's problem to fix, not yours: you still get your shares, either from the original seller or through a buy-in. The bigger takeaway is what this machinery says about a stock. A name thin enough to make gagal serah a real risk is also a name where a large order of yours could move the price more than you expect, or where you could struggle to sell in a hurry if you needed the cash.
Before placing a large order in a stock you have not traded before, check how actively it actually trades. NetWort's Market page shows a live IDX heatmap and sentiment pulse, so you can see at a glance which stocks are trading with real daily volume, the same kind of liquidity IDX itself is screening for when it decides which stocks are safe enough to open up for short selling.