Auction

Auction trading is a process exchanges like NSE or BSE use to resolve payment defaults or short delivery of shares. It ensures the buyer still receives their shares.

• Two triggers: failure to fulfil pay-in obligation, or short delivery of shares.
• Auction window: T+2 day, between 2 PM and 2:45 PM.
• Bid limit: cannot exceed 20% of the T+1 day's closing price.
• Delivery to buyer: completed on the T+3 day.
• If no seller is found, the exchange does a "close-out" — settling in cash instead of shares.
• Applies to commodities too, initiated by the MCX.

Auction trading is a process exchanges use to resolve two specific situations: payment defaults and short delivery of shares. When a seller fails to deliver shares by the agreed date, the exchange steps in to manage the shortfall.

This mechanism applies to the equity segment through the NSE or BSE, and to commodities through the MCX.

Two scenarios trigger the auction process.

Scenario 1: Failure to fulfil pay-in obligation

This happens when an investor sells shares but fails to deliver them by the agreed date. Common reasons include:

• Discrepancies in the delivery slip or transfer details.
• Shares already pledged as collateral for a loan or margin requirement, making them inaccessible to the seller.

Example: An investor sells shares of a company but hits an error in the delivery paperwork, or has already pledged those shares as collateral — either way, delivery fails on the due date.

Scenario 2: Short delivery of shares
 

This happens when a trader takes a short position (sells shares they don't own, expecting to buy back lower) but fails to close that position within the same trading day. Reasons can include adverse market movement, technical issues, or a lack of available shares to buy back.

Example: A trader shorts 100 shares expecting the price to fall, but the price rises instead by day's end — leaving the short position open and delivery incomplete.

Note- The securities and companies referenced above are hypothetical examples only and not a recommendation.

The exchange facilitates buying and selling of the undelivered or short-delivered shares. Interested brokers submit bids, and the auction mechanism selects a winner based on set price limits.

During the auction trading process:

• The exchange facilitates the buying and selling of the shares that were:
  • Not delivered or
  • Not covered due to short delivery
• Bids are submitted by interested parties.
• The auction mechanism determines the winning bid based on specified criteria, such as price limits.
• The exchange then ensures that the shares are delivered to the buyer, completing the transaction and fulfilling the obligations of the seller.

Auction trading is the mechanism NSE, BSE, or MCX use to resolve payment defaults and short deliveries, ensuring transactions still complete even when a seller can't deliver on time. The process runs on a fixed timeline — bidding on the T+2 day, delivery by T+3 — with bid limits capped at 20% of the prior day's closing price.

When no seller steps in, a close-out settles the trade in cash instead, protecting the buyer's position. This structured fallback is what keeps the market's settlement process reliable even when individual transactions fail.