CAS Market Data
Effective Date: September 4, 2026
Closing Auction Session (CAS) data is now available on both the REST and WebSocket market data surfaces. While the closing auction runs, you can read the price the auction is discovering and the quantities behind it — from a single REST call, or live over the WebSocket feed — instead of waiting for the closing price to be published.
What's New?
Full Market Quotes V3 (REST)
- Live closing auction values on the Full Market Quotes V3 endpoint: Each symbol now carries the indicative equilibrium price and quantity, the total and market indicative imbalance quantities, the reference price, and CAS eligibility. The Full Market Quotes V3 API returns the complete market data snapshot for up to 500 instruments in a single request.
Market Data Feed V3 (WebSocket)
-
Live closing auction values on the full and full_d30 feeds: These feeds now carry the same live closing auction values as above, plus the indicative equilibrium price wherever last-traded-price details appear in the feed.
-
Market status now reports CAS and pre-open session state: Market status updates now include each segment's current closing auction and pre-open session status.
New Fields (REST)
| Field | Type | Description |
|---|---|---|
| indicative_equilibrium_price | number | The specific price at which the maximum possible number of shares can be matched based on the current order book |
| indicative_equilibrium_quantity | integer | The exact total number of shares that will successfully execute at the calculated indicative equilibrium price |
| indicative_imbalance_quantity_total | integer | The net excess buy or sell quantity that remains unmatched at the indicative equilibrium price |
| indicative_imbalance_quantity_market | integer | The portion of that unmatched total quantity that originates exclusively from unpriced market orders |
| reference_price | number | The base price used to calculate the applicable price bands and circuit filters for the session |
| cas_eligible | boolean | Whether the symbol is permitted to participate in any Call Auction Session |
| prev_close_price | number | The close price of the symbol from the previous session of trading |
| year_high | number | The highest price of the symbol over the trailing year |
| year_low | number | The lowest price of the symbol over the trailing year |
| previous_oi | number | The open interest of the symbol from the previous session (only F&O) |
New Fields (WebSocket)
| Field | Type | Description |
|---|---|---|
| iep | number | Indicative Equilibrium Price: The specific price at which the maximum possible number of shares can be matched based on the current order book |
| rp | string | Reference Price: The base price used to calculate the applicable price bands and circuit filters for the session |
| ieq | string | Indicative Equilibrium Quantity: The exact total number of shares that will successfully execute at the calculated indicative equilibrium price |
| iiqTotal | string | Total Indicative Imbalance Quantity: The net excess buy or sell quantity that remains unmatched at the indicative equilibrium price. Can be negative |
| iiqM | string | Market Indicative Imbalance Quantity: The portion of that unmatched total quantity that originates exclusively from unpriced market orders |
| casEligible | boolean | CAS Eligible: Whether the instrument is permitted to participate in any Call Auction Session |
| ltpc.iep | number | Indicative Equilibrium Price: Present on LTPC wherever it appears in the feed; the same indicative equilibrium price, only while the pre-open or closing auction session is active |
The WebSocket feed now gives you live CAS timing status directly, as covered in the Market Status section of the Market Data Feed V3 documentation.
Further Reading
- Full Market Quotes V3 API — the REST endpoint reference, response schema and sample code.
- Full Market Quotes API — the V2 endpoint, which continues to work unchanged.
- Market Data Feed V3 — the WebSocket feed reference, including the Closing Auction Session (CAS) Fields and Market Status sections.
- Closing Auction Session (CAS) support — the session, its phases and the order-flow restrictions that apply during it.
- Pre-Open Session statuses — the new
preOpenSessionStatusvalues. - Developer Community — questions and feedback.
Thank You
Thank you for building with the Upstox Developer API. Share any feedback on these updates with us on the Developer Community.