Short answer: Borsa Istanbul T+1 settlement has no announced start date as of 5 November 2026: shares still settle at Takasbank on T+2, with a 16:45 deadline. Exchange letters 38907 and 50492 require all T+1 preparation to be finished by 31 December 2026, and 50492 sets six go-live rehearsals, the first planned for 27 August 2026, with participation mandatory from 14 September 2026. Neither letter gives a go-live date.
The move to one-day settlement has a preparation deadline but no start date, and that gap matters most to the people Borsa Istanbul addressed its letters to: members, the Turkish Capital Markets Association, data vendors, software suppliers to members and listed companies.
Everything here was checked on 5 November 2026 against Borsa Istanbul, Takasbank and MKK (Central Registry Agency) documents. This guide forecasts no date and names no broker or custodian.
What is Takasbank and what does it do at Borsa Istanbul?
Takasbank (İstanbul Takas ve Saklama Bankası A.Ş.) is the central clearing institution for Borsa Istanbul trades, the central counterparty on its main markets and a licensed bank (opens in a new tab).
| Institution | Role | Basis |
|---|---|---|
| Borsa Istanbul | Matches orders and passes trades to clearing | Exchange rules |
| Takasbank | Nets positions, stands as buyer to every seller and seller to every buyer, settles cash | Law 6362, Articles 77 and 78 |
| MKK, the central depository | Keeps the electronic record of shares and the rights attached to them | Law 6362, Articles 80 and 81 |
| Member firm | Owes Takasbank; Takasbank does not answer for what the member owes its clients | Law 6362, Article 78(2) |
Takasbank's central counterparty page dates that role to 19 June 2017 on the Equity Market and 3 March 2014 on VİOP, the derivatives market, whose products are leveraged: losses can exceed the margin deposited. Because of Article 78(2) of Law No. 6362, the guarantee does not reach an investor whose broker fails; how to buy Turkish stocks covers that risk. Article 79 makes settlement instructions irrevocable even if a member is suspended or enters liquidation.
Takasbank also operates TEFAS, covered in Turkish mutual funds and TEFAS, and the Takasbank Money Market (opens in a new tab) (Takasbank Para Piyasası), which its page says has matched members holding surplus funds with members needing funds since 1996.
Borsa Istanbul settlement today: T+2 and the 16:45 deadline
Shares settle on T+2, delivery versus payment, and a member that has not closed its cash and securities debts by 16:45 that day is in default without notice, according to Takasbank's Equity Market procedure (amendments through 29 August 2026).
| Step | When | Article |
|---|---|---|
| Trade corrections (account fields only) and position transfers | Until market close on T+1 | 25, 26 |
| Settlement instructions created | End of T+1 | 28 |
| Instructions visible to members | Start of T+2 | 28 |
| Net and gross cash and securities debts closed | 09:00 to 16:45 on T+2 | 18 |
| Late performance: default interest coefficient 1, then 3 | To 17:30, then from 17:31 or later days | 68 |
Netting is multilateral and daily, per security, with client and portfolio positions kept apart (Article 22). Under delivery versus payment, a member that has not met its debts does not receive its credits, although partial delivery can earn partial payment (Article 23). Securities debts close when shares move from the member's pool account at MKK to Takasbank's settlement pool (Article 30).
Gross settlement, half days and other exceptions
Netting can be switched off and half days never settle, so a settlement date is not always the trade date plus two business days.
- Gross settlement (brüt takas). The Capital Markets Board or the exchange can order it by market, security or investor (Articles 22 and 31). The member then owes all purchases in cash and all sales in shares, and credits are paid only after the deadline, so a same-day purchase cannot cover a same-day sale.
- Half days. No settlement takes place. A settlement date falling on a half day moves to the next full business day, and half-day trades merge with the previous day's and settle on the second business day after the half day (Article 18/3).
From the official 2026 holiday table: 19 March 2026 was a half day, followed by a closure on 20 March. It put trades of Tuesday 17 March on Monday 23 March, and trades of Wednesday 18 and Thursday 19 March together on Tuesday 24 March. Session times are in Borsa Istanbul trading hours and holidays.
Borsa Istanbul T+1: what the letters say, with dates
Borsa Istanbul has set a preparation deadline of 31 December 2026 and a rehearsal program, and as of 5 November 2026 it has not published a go-live date.
| Date | Document | What it says |
|---|---|---|
| 5 May 2025 | Exchange announcement | Opens an assessment of T+1. Cites the US move of 28 May 2024 and a target of 11 October 2027 for the EU, Switzerland and the UK |
| 29 August 2025 | Letter 38907 | All T+1 work (analysis, development, testing) must be complete by 31 December 2026; test environments from 5 January 2026 |
| 19 December 2025 | Letter 42203 | T+1 test environment open seven days a week from 5 January 2026. Technology companies get special member codes to test across Borsa Istanbul, Takasbank and MKK. The work also covers derivatives based on these instruments |
| 30 March 2026 | MKK announcement 2523 | For issuers: in cash dividends, rights issues and bonus issues, the record date moves onto the ex-date and the payment date from T+2 to T+1 |
| 5 June 2026 | MKK announcement 2542 | Scenario tests follow free testing; MKK's test system MKSTEST opens on 8 June with data of 5 June |
| 20 August 2026 | Letter 50492 | Six go-live rehearsals, two on test data and four on live data. First planned for 27 August 2026; participation mandatory from the third, starting 14 September 2026. Test steps: sheets 1 to 5, 7 and 8 of the Connect scenario file of 3 June 2026 |
| 3 November 2026 | Notice 52753 | BISTECH 3.15, planned for 9 November 2026, is postponed with a new date to follow. T+1 is not mentioned |
What has not been announced
- A go-live date. Letter 50492 refers to the go-live date without stating one, and the exchange's technical and general announcement lists showed no newer T+1 item on 5 November 2026.
- New hours. No document read says whether 16:45 stays; Takasbank's board sets the deadline after consulting the exchange (procedure Article 18(5)).
- New rules. Takasbank's procedure file dated 1 September 2026 still describes the T+2 sequence, and its share market page, read 5 November 2026, says T+2 and does not mention T+1.
- A T+1 holiday table. The exchange's holidays page, read the same day, ends at 2026.
- A link to BISTECH 3.15. Notices 50491, 51227 (opens in a new tab) and 52753 do not mention T+1, so do not assume the two projects move together.
T+1 would not be new to this market: the chronology in the Equity Market Procedure (revision 54, 21 September 2026) records settlement cut to one day on 6 October 1990 and moved to T+2 on 14 July 1994.
What T+1 would compress: hours, time zones and FX funding
Keeping today's hours would cut the time from the close to the deadline by a full day; the figures below are arithmetic, not rules.
Hypothetical, assuming the 16:45 deadline stays: a trade at the 18:10 close on a Monday has 46 hours 35 minutes until the deadline under T+2 and 22 hours 35 minutes under T+1, with no holiday in between. In other centers, 16:45 Istanbul time (UTC+3 all year) is 13:45 GMT or 14:45 BST in London and 08:45 EST or 09:45 EDT in New York.
None of the letters addresses foreign-exchange funding. On those hypothetical hours, a New York manager would need lira in place by 08:45 or 09:45 on the morning after the trade, and a custodian's own instruction cut-off would come earlier. MKK's 2025-2026 custodian questionnaire (opens in a new tab) describes a separate delivery-versus-payment flow for broker-to-custodian trades, such as those of foreign institutions, so the time for broker-custodian matching would shrink as well.
If Turkey moved before the 11 October 2027 target the exchange cites for the EU, Switzerland and the UK, a fund selling European shares to buy Turkish ones could owe lira before the sale proceeds arrive. Ask each custodian for its lira cut-off.
T+1 checklist for software owners
Make the settlement cycle and the calendar data rather than code, then test every downstream date and report in the T+1 environment.
| Area | What breaks | What to do |
|---|---|---|
| Settlement dates | A hard-coded +2 in order, portfolio and tax-lot logic | Store the cycle with an effective trade date. No published rule covers the cutover day, so test last T+2 and first T+1 trades falling due together |
| Holiday calendars | Half-day merging written for two days | Load the official table and alert on any difference; no 2027 or T+1 table exists yet |
| Cash projections | Buying power and funding forecasts run a day late | Derive them from the effective cycle; gross-settled shares need full cash a day earlier |
| Corporate actions | Entitlement and payment dates built on T+2 | Retest record date logic and client notices against MKK 2523 |
| Trade corrections | Articles 25 and 26 run to the T+1 market close, later than a 16:45 deadline that same day | Make these windows settings and watch for amended Takasbank text |
| MKK reconciliation | Jobs timed for instructions that appear at the start of T+2 | Move the job, rerun it against MKSTEST and compare with drop copies as in broker API integration |
| Derivatives | Stock futures and options deliver on T+2 under the VİOP procedure (revision 70, 1 July 2026) | Letter 42203 brings them into the work, so do not fork the logic |
This function reproduces the official 2026 equity holiday table for all 17 trade dates it lists from March to October, with one rule: count the days that are not weekends, closures or half days.
from datetime import date, timedelta
def day(md):
return date.fromisoformat("2026-" + md)
# Borsa Istanbul equity holiday table 2026
CLOSED = {day(x) for x in "01-01 03-20 04-23 05-01 05-19 05-27 05-28 05-29 07-15 10-29".split()}
HALF = {day(x) for x in "03-19 05-26 10-28".split()} # trading, no settlement
def settlement_date(trade, cycle):
if trade.weekday() > 4 or trade in CLOSED:
raise ValueError("not a trading day")
d = trade
for _ in range(cycle):
d += timedelta(days=1)
while d.weekday() > 4 or d in CLOSED or d in HALF:
d += timedelta(days=1)
if not d.year == 2026:
raise ValueError(f"no {d.year} holiday table")
return d
# Trade date, settlement date, as printed in the official table
OFFICIAL = """03-17 03-23 03-18 03-24 03-19 03-24 04-21 04-24 04-22 04-27
04-29 05-04 04-30 05-05 05-15 05-20 05-18 05-21 05-22 06-01 05-25 06-02
05-26 06-02 07-13 07-16 07-14 07-17 10-26 10-30 10-27 11-02 10-28 11-02""".split()
rows = [(day(a), day(b)) for a, b in zip(OFFICIAL[::2], OFFICIAL[1::2])]
print("matched", sum(settlement_date(t, 2) == s for t, s in rows), "of", len(rows))
# Hypothetical T+1 on today's holiday logic; no T+1 table has been published
for md in ("10-26", "10-27", "10-28"):
t = day(md)
print(t, "T+2", settlement_date(t, 2), "hypothetical T+1", settlement_date(t, 1))Output, run on 5 November 2026 with Python 3.11 and no dependencies:
matched 17 of 17
2026-10-26 T+2 2026-10-30 hypothetical T+1 2026-10-27
2026-10-27 T+2 2026-11-02 hypothetical T+1 2026-10-30
2026-10-28 T+2 2026-11-02 hypothetical T+1 2026-10-30The T+1 column is hypothetical: it shows only that the calendar must be an input, because the exchange may publish a different rule for days around half days. The project and product analysis page describes outside review of a change like this.
Frequently asked questions
When does Borsa Istanbul move to T+1?
No go-live date had been published as of 5 November 2026. Letters 38907 and 50492 require all preparation to be complete by 31 December 2026, which is a preparation deadline rather than a start date.
Is Takasbank a bank or a clearing house?
Both. It holds a banking license and is the central clearing institution for Borsa Istanbul, acting as central counterparty on markets including shares and VİOP.
Will Takasbank pay me if my broker fails?
No. Article 78 of Law No. 6362 says clearing institutions are not responsible for their members' obligations to customers. The Investor Compensation Center is a separate regime.
Does T+1 affect VİOP?
Letter 42203 says the work also covers derivatives based on equity market instruments. The VİOP procedure of 1 July 2026 still shows T+2 for physical delivery of stock futures and options.
Is BISTECH 3.15 part of the T+1 project?
Nothing published says so: notices 50491, 51227 and 52753, including the 3 November 2026 postponement, do not mention T+1.
Sources
- Borsa Istanbul letter 50492, 20 August 2026: participation in T+1 go-live rehearsals (Turkish) (opens in a new tab)
- Borsa Istanbul letter 38907, 29 August 2025: shortening the settlement cycle (Turkish) (opens in a new tab)
- Borsa Istanbul letter 42203, 19 December 2025: new T+1 test environment (Turkish) (opens in a new tab)
- Borsa Istanbul announcement, 5 May 2025: evaluation of moving from T+2 to T+1 (opens in a new tab)
- Borsa Istanbul notice 52753, 3 November 2026: BISTECH 3.15 postponed (Turkish) (opens in a new tab)
- Borsa Istanbul: technical announcements list (Turkish) (opens in a new tab)
- MKK announcement 2523, 30 March 2026: T+1 project information for issuers (Turkish) (opens in a new tab)
- MKK announcement 2542, 5 June 2026: T+1 scenario tests (Turkish) (opens in a new tab)
- Takasbank: Equity Market clearing and central counterparty procedure, amendments through 29 August 2026 (Turkish) (opens in a new tab)
- Takasbank: Equity Market general definition, T+2 and 16:45 (Turkish) (opens in a new tab)
- Takasbank: Central counterparty service and start dates by market (Turkish) (opens in a new tab)
- Borsa Istanbul: Equity Market Procedure, revision 54, 21 September 2026 (Turkish) (opens in a new tab)
- Borsa Istanbul: Equity Market 2026 holiday table with settlement dates (Turkish) (opens in a new tab)
- Capital Markets Law No. 6362, Articles 77 to 81 (Turkish) (opens in a new tab)
- Borsa Istanbul: VİOP Procedure, revision 70, 1 July 2026 (Turkish) (opens in a new tab)
This guide is general information, not investment, legal or tax advice. Amounts, rates and rules in Turkey change often: check the date given for each figure and the official source before you rely on it, and ask a licensed adviser about your own situation. Sources, checks and corrections: see the editorial policy.