The single most useful thing to know about Taiwan’s futures expiry is this: the final settlement price for TAIFEX index futures and options is not the TAIEX closing print on expiry day. It is an arithmetic average of index values sampled across the last 30 minutes of the cash session, from 13:00 to 13:30 Taipei time, on the third Wednesday of the contract month — the contract’s last trading day. That one design choice — averaging instead of a single print — explains most of what you will see on expiry day, from why the settlement price never exactly matches the close to why ‘banging the close’ is far harder in Taipei than in single-print markets.
Interest in this mechanism tends to spike around heavily watched expiries, and the August 2026 cycle drew exactly that kind of attention: the TAIEX closed at 44,719.35 on the last trading day, 2026-08-19, and the most recent published TAIFEX positioning data — dated to that same session, since the series is released with a one-session lag — showed foreign institutions net short 81,501 Taiwan index futures contracts. This guide is not about that week — it is about the machinery that produces such weeks, which repeats every month on the same calendar.
The contract calendar: everything hangs off the third Wednesday
The Taiwan Futures Exchange (TAIFEX) lists futures and options on the Taiwan Stock Exchange Capitalization Weighted Stock Index — universally called the TAIEX, or in local shorthand the jiaquan zhishu (加權指數, ‘the weighted index’). The flagship contract is the TAIEX futures, known locally as taizhiqi (台指期, ‘Taiwan index futures’) and by the exchange ticker TX.
- Listed months. At any time, TX lists the spot (current) month, the next two calendar months, and the next three quarterly months from the March–June–September–December cycle — six contract months in total. So there is always a ‘front month’ and a ‘second month’ trading side by side.
- Last trading day. The third Wednesday of the contract month. This is the day the final settlement price is calculated. If that day is a holiday, the exchange shifts it per its calendar rules — check TAIFEX’s published trading calendar rather than assuming.
- Final settlement day. Under TAIFEX contract specifications, the same day as the last trading day. The settlement price is computed that afternoon, and the resulting cash difference flows through margin accounts. Contracts are cash-settled in New Taiwan dollars; nothing is delivered.
- Expiry-day hours. TAIFEX index futures normally trade a day session of 8:45–13:45, fifteen minutes past the 13:30 cash-market close. On its last trading day, however, the expiring contract stops trading at 13:30, aligned with the cash close — the extra 13:30–13:45 window applies only to non-expiring months.
Note that not every Wednesday expiry is the monthly one: TAIFEX also lists weekly TAIEX options, which ordinarily cover Wednesdays other than the monthly contract’s third Wednesday. The third Wednesday is when the monthly futures and the monthly options expire together — which is why it is the heavyweight date on the calendar.
| Contract | Ticker | Multiplier | Last trading day | Settlement basis |
|---|---|---|---|---|
| TAIEX futures | TX | NT$200 per index point | 3rd Wednesday | 30-min average, 13:00–13:30 |
| Mini-TAIEX futures | MTX | NT$50 per index point | 3rd Wednesday | Same as TX |
| Micro TAIEX futures | TMF | NT$10 per index point | 3rd Wednesday | Same as TX |
| TAIEX options (monthly) | TXO | NT$50 per index point | 3rd Wednesday | Same as TX |
How the final settlement price is set
An average, not a print
The final settlement price — jiesuan jia (結算價) — is computed as the simple arithmetic average of the TAIEX values disseminated by the Taiwan Stock Exchange during the final 30 minutes of the cash session on the last trading day, roughly 13:00 to 13:30. The TWSE publishes index updates every few seconds, so the average is taken over hundreds of index snapshots, not a handful. TAIFEX publishes the official figure on its website the same afternoon, on its final settlement price page.
Two practical consequences follow immediately:
- The settlement price will not equal the 13:30 close. If the index trends during the window, the average sits somewhere between the 13:00 level and the close. A market falling steadily through the window settles above its close; a market rallying into the bell settles below it. In-the-money options are exercised against the average, so an option that looks in the money versus the closing print can expire worthless versus the settlement price, and vice versa.
- You cannot trade the settlement price directly. No single transaction occurs at the average. A hedger who needs to match it must execute across the whole window — in practice, a time-weighted (TWAP-style) unwind in the cash basket or in the futures themselves between 13:00 and 13:30. This is also the common market interpretation of why expiry-day activity concentrates into the final half hour: participants widely attribute that pattern to index-arbitrage books unwinding against the calculation window, though the attribution is an interpretation of flows rather than a published statistic.
Why averaging blunts manipulation
Markets that settle derivatives on a single print — one closing auction, one special opening quotation — concentrate all the incentive to manipulate into one moment. A player with a large expiring position needs to move the index for only seconds, and every point of movement pays off on the full position. Taiwan’s 30-minute average changes that arithmetic in three ways:
- Cost scales with time. Moving a 30-minute average requires holding the index away from equilibrium for the whole window, in the cash market, against the full weight of arbitrage capital leaning the other way. Pushing heavyweight index names for half an hour costs a multiple of pushing them for one auction.
- Each snapshot is diluted. With index values sampled every few seconds across 30 minutes, a burst of aggressive orders distorts only the handful of snapshots it touches — a rounding error in the average.
- Concentration limits the lever anyway. The TAIEX is top-heavy — TSMC alone is by far the largest weight, and foreign investors held 69.16% of its shares as of the 2026-08-19 TWSE data — so any attempt to push the index runs straight into the deepest, most heavily arbitraged stocks on the exchange.
The design does not eliminate expiry-day turbulence — positioning unwinds are real and can be violent — but it converts ‘settlement manipulation’ from a seconds-long trade into a sustained, expensive, and highly visible cash-market operation.
Worked example: reading foreign net open interest around an expiry
The most-watched positioning number in Taiwan is foreign institutions’ net open interest in TX futures, published daily by TAIFEX. Here is an actual figure from around an expiry and how to read it, step by step.
The figure: as of the 2026-08-19 session — the August 2026 last trading day, and the most recent session for which TAIFEX had published data — foreign investors’ net open interest in TX futures was −81,501 contracts (net short), with a day’s net volume of +749 contracts.
- Convert contracts to notional. TX is NT$200 per index point. With the TAIEX at 44,719.35 (2026-08-19 close), one contract represents roughly NT$8.9 million. So 81,501 contracts is roughly NT$730 billion of index exposure — around US$23 billion at the exchange rate of roughly 31.9 TWD per USD prevailing at that date.
- Check which contract it sits in. On the last trading day, the expiring month’s open interest collapses to zero by definition. But mind the reporting cutoff: this figure is dated to the expiry session itself and published with the usual one-session lag, and the headline number alone does not break out contract months. Before concluding that a large net short was rolled or rebuilt into the new front month — rather than reflecting positions as of the published cutoff — check TAIFEX’s contract-month breakdown.
- Do not read it as a pure directional bet. Foreign institutions hold enormous Taiwan cash portfolios (as of 2026-08-19 TWSE data, 69.16% of TSMC, 55.74% of MediaTek, 40.47% of Hon Hai). A futures short is often a hedge on that cash book rather than an outright bearish wager. The signal is in the change more than the level: rapid swings in the number around expiry tell you hedges are being rebuilt or lifted.
- Cross-check with options. The TAIFEX put/call ratio on open interest stood at 117.16% as of 2026-08-17 — more put OI than call OI. Readings above roughly 100% typically indicate a hedged or defensive options book; read it alongside the futures OI rather than in isolation, and remember both series are published with a one-session lag.
Rollover: how open interest migrates
In the week before the third Wednesday, positions migrate from the expiring front month to the second month. The mechanics worth watching:
- Calendar spreads do the work. Most rolling happens via simultaneous sell-front/buy-next (or the reverse) spread trades, so the roll shows up as front-month OI shrinking while second-month OI grows, day by day, with total OI roughly stable.
- The spread price is information. The price gap between the two months reflects dividend expectations and funding. A roll that suddenly cheapens or richens signals one side (often the hedgers) paying up to move size.
- Volume leadership flips before expiry. Typically a day or two before the third Wednesday, the second month overtakes the expiring month in volume. By expiry morning, the old front month is mostly arbitrage books positioning for the 13:00–13:30 window.
- Post-expiry OI resets your baseline. Compare positioning figures only within the same contract cycle, or you will mistake the mechanical expiry drop in OI for position-cutting.
Common mistakes to avoid
- Marking expiring options against the close. Exercise is against the 30-minute average. Near-the-money strikes routinely flip in-versus-out of the money between the average and the closing print.
- Assuming the expiring future trades until 13:45. It stops at 13:30 on the last trading day. Orders resting for the 13:30–13:45 futures-only window will apply to other months, not the expiring one.
- Treating foreign net shorts as a crash forecast. As in the worked example above, much of that book hedges cash holdings. Track the change, not the level, and note the one-day publication lag.
- Forgetting holiday shifts. When the third Wednesday collides with a Taiwan holiday, TAIFEX’s calendar governs. Never hard-code ‘third Wednesday’ in a model without a calendar check.
FAQ
Is the TAIFEX final settlement price the same as the TAIEX close on expiry day?
No. It is the arithmetic average of index values disseminated during the last 30 minutes of the cash session (13:00–13:30 Taipei) on the third Wednesday, the last trading day. It usually lands near, but almost never exactly on, the closing print, and the gap widens whenever the index trends into the close. TAIFEX publishes the official figure the same afternoon.
When does the cash actually move?
Contracts are cash-settled in New Taiwan dollars. The final settlement price is calculated on the last trading day (the third Wednesday), and under TAIFEX contract specifications the final settlement day is that same day — the resulting difference is credited or debited through margin accounts as part of that day’s settlement.
Do weekly options settle the same way?
Yes — TAIFEX’s weekly TAIEX options use the same average-based settlement mechanism on their own Wednesday expiries, which ordinarily cover Wednesdays other than the monthly contract’s third Wednesday. The third Wednesday stacks the monthly futures and monthly options onto one date, which is why it dominates expiry-week flows.
Where do I find the official numbers?
TAIFEX publishes final settlement prices, daily open interest by investor type (including the foreign net OI series), and put/call ratios on its website, generally with a one-session lag for the positioning data. Cash-market index data and foreign ownership figures come from the TWSE.
Sources
- Taiwan Futures Exchange — contract specifications, trading calendar, final settlement prices, institutional open interest: www.taifex.com.tw
- Taiwan Stock Exchange — TAIEX index data and foreign ownership statistics: www.twse.com.tw/en
- TWSE OpenAPI — machine-readable market data: openapi.twse.com.tw
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.