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IDX Indonesia Stock Exchange API

idx-indonesia-stock-exchange-apisource

Use when routing equity orders to the Indonesia Stock Exchange JATS system, enforcing four-letter tickers, Fraksi Harga tick sizes anchored to the previous close, 100-share board lots and segment designation.

Domain
Global Market Integration
Version
2.0.0
Reading
5 min
Hands off to
4
Handed off from
0
License
Apache-2.0
CoversJATS (Jakarta Automated Trading System)IDX FIX GatewayPython Dataclasses

When to Use

Use this skill in Southeast Asian market execution algorithms, IDX gateways, and JATS trading systems. Trading on the Indonesia Stock Exchange (IDX / BEI) requires strict adherence to JATS order rules: 4-letter ticker symbols (e.g. BBCA Bank Central Asia, TLKM Telkom), market segment designations (RG Pasar Reguler, TN Pasar Tunai, NG Pasar Negosiasi), Fraksi Harga tick sizes, mandatory 100-share Board Lot multiples, a per-order volume cap, and the asymmetric ARA/ARB Auto Rejection band.

When NOT to Use

  • Non-equity IDX instruments: rights (TLKM-R), warrants (TLKM-W), structured warrants, ETFs, bonds and derivatives have their own trading rules and are deliberately rejected by the ticker validator.
  • As a replacement for exchange-side controls: this is a client-side pre-trade filter. JATS remains authoritative and can reject an order this engine approves — trading halts, suspensions, short-sale restrictions, and the pre-opening/closing auction phases are not modelled.
  • Intraday tick re-derivation: do not call the engine with a live last-traded price in reference_price. The Fraksi Harga and Auto Rejection band are both anchored to the previous close for the whole trading day.

Prerequisites

  • IDX order request (ticker, board_type: RG/TN/NG, side, price, quantity, reference_price).
  • A reference price (Acuan Harga) source: the previous Pasar Reguler closing price, or the theoretical price after a corporate action, or the listing price on a debut.
  • Optional: the instrument's listing board (MAIN, DEVELOPMENT, NEW_ECONOMY, ACCELERATION, WATCHLIST) and listed share count, for the correct Auto Rejection percentages and the 5%-of-listed-shares volume cap.
  • Current IDX Peraturan Nomor II-A schedules — see references/standards.md for the dated tables in force.

Workflow

  1. Ticker & Market Segment Normalization:
    • Format ticker to 4 uppercase ASCII letters (BBCA, TLKM); reject suffixed instruments (-R, -W).
    • Validate market segment (RG, TN, NG) and order side (BUY, SELL).
    • Validate that reference_price is finite and strictly positive before using it as a divisor or band anchor — a zero or missing previous close must raise, never silently produce a band of zero width.
  2. Segment Branch — decide which rules even apply:
    • RG / TN trade on the continuous JATS order book: round lot, Fraksi Harga, volume cap and Auto Rejection all apply.
    • NG (Pasar Negosiasi) is bilaterally negotiated: none of those four apply. Do not reject a negotiated block for being an odd lot or for pricing outside the ARA/ARB band — that is a false rejection of a legitimate trade.
  3. IDX Fraksi Harga (Tick Size) Audit:
    • Select the tick from the reference price, not the order price. IDX fixes the tick for a full trading day from the previous close and only re-derives it on the next trading day:
      • $P_{ref} < \text{Rp } 200 \implies \Delta P = \text{Rp } 1$.
      • $\text{Rp } 200 \le P_{ref} < \text{Rp } 500 \implies \Delta P = \text{Rp } 2$.
      • $\text{Rp } 500 \le P_{ref} < \text{Rp } 2,000 \implies \Delta P = \text{Rp } 5$.
      • $\text{Rp } 2,000 \le P_{ref} < \text{Rp } 5,000 \implies \Delta P = \text{Rp } 10$.
      • $P_{ref} \ge \text{Rp } 5,000 \implies \Delta P = \text{Rp } 25$.
    • Verify the order price is a whole number of Rupiah and an exact integer multiple of $\Delta P$.
  4. Minimum Price Floor: reject prices below Rp 50 on the Main/Development/New Economy boards, or below Rp 1 on the Acceleration/Watchlist boards.
  5. Board Lot Sizing (1 Lot = 100 Shares): for RG and TN, verify quantity is a multiple of $100$ shares.
  6. Order Volume Auto Rejection: reject orders larger than $\min(50{,}000 \text{ lots},\ 5% \text{ of listed shares})$. With no listed-share count available, enforce the 50,000-lot cap and record that the 5% leg was not evaluated.
  7. Price Auto Rejection (ARA / ARB) Audit — asymmetric since 8 April 2025:
    • Main/Development/New Economy: ARA $= +35%$ ($P_{ref} \le \text{Rp } 200$), $+25%$ ($\text{Rp } 200 < P_{ref} \le \text{Rp } 5{,}000$), $+20%$ ($P_{ref} > \text{Rp } 5{,}000$); ARB $= -15%$ in every band.
    • Acceleration/Watchlist: $\pm \text{Rp } 1$ for $P_{ref} \le \text{Rp } 10$, else $\pm 10%$.
    • Clamp the lower bound to the minimum price floor.
  8. Audit Report Generation: Output structured IdxOrderReport.

Full procedure: see references/workflows.md. Standards reference: see references/standards.md. Printable pre-flight checklist: see assets/checklist.md.

Common Pitfalls

  • Deriving the tick from the order price: IDX fixes the Fraksi Harga from the previous closing price for the whole trading day. With a Rp 1,990 close (tick Rp 5), Rp 2,005 is a valid price all day even though its own band implies Rp 10; with a Rp 2,010 close (tick Rp 10), Rp 1,995 is invalid all day. Deriving the tick from the order price produces false rejections in one direction and orders JATS will reject in the other.
  • Treating ARA and ARB as symmetric: since 8 April 2025 ARB is a flat 15% while ARA is 20–35% by price band. A symmetric $\pm 25%$ check simultaneously waves through sell orders IDX will auto-reject and blocks buy orders IDX would accept.
  • Applying order-book rules to Pasar Negosiasi: NG is exempt from round lots, Fraksi Harga, the volume cap and Auto Rejection. Rejecting a negotiated block for an odd lot or an off-band price blocks a legitimate trade.
  • Ignoring the listing board: an Acceleration or Watchlist (Papan Pemantauan Khusus) stock has a $\pm 10%$ band and a Rp 1 floor, not the main-board 35/25/20% and Rp 50. Applying main-board limits to a Watchlist name mis-sizes the band by a factor of two or more.
  • Unvalidated reference price: a missing or zero previous close divides by zero or collapses the Auto Rejection band. Raise on it; never fall back to the order price.
  • Submitting invalid tickers: 5-letter, numeric, or suffixed codes (TLKM-R) cause instant gateway rejection.
  • Odd-lot submission to the Regular market: routing non-100-share multiples to RG/TN.
  • Forgetting the per-order volume cap: an order above 50,000 lots (or 5% of listed shares, whichever is smaller) is auto-rejected on size alone, regardless of price.

Verification

  • Instantiate IdxStockExchangeApiEngine. Route a Bank Central Asia order (ticker="BBCA", board_type="RG", Price $=\text{Rp } 10,000$, Qty $=500$ shares / 5 Lots, Ref Price $=\text{Rp } 10,000$). Verify the engine validates the 4-letter ticker, selects $\Delta P = \text{Rp } 25$ from the reference price, confirms the 5-lot size, computes the asymmetric band $\text{Rp } 8{,}500 - \text{Rp } 12{,}000$, and returns IDX_ORDER_VALIDATED.
  • Confirm the reference-price anchoring: an order at Rp 2,005 against a Rp 1,990 reference price must be accepted (tick Rp 5), and an order at Rp 1,995 against a Rp 2,010 reference price must be rejected with INVALID_TICK_SIZE (tick Rp 10).
  • Confirm asymmetry: against a Rp 1,000 reference price, Rp 1,200 (+20%) is accepted while Rp 800 (−20%) returns AUTO_REJECTION_EXCEEDED.
  • Run the test suite:
python -m unittest discover -s skills/idx-indonesia-stock-exchange-api/scripts

Verify it, from the repository root

python -m unittest discover -s skills/idx-indonesia-stock-exchange-api/scripts

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