Day Order, IOC and Other Common Order Validities

Order price tells the exchange what price you are willing to accept. Order validity tells the exchange how long the instruction should remain alive. That second dimension matters because the same limit price can behave very differently depending on whether the order is allowed to wait for hours or is cancelled almost immediately.

For Indian equity-market beginners, the two most important time conditions to understand are DAY and IOC. A DAY order can remain active during the trading day until it is filled or the session ends. An Immediate or Cancel order tries to execute immediately and automatically cancels any unmatched balance.

Price condition and time condition are different decisions

A market order or limit order answers a price question. A DAY or IOC instruction answers a time question. Thinking in two dimensions prevents a common beginner mistake: assuming that ‘limit’ automatically means the order waits indefinitely, or that ‘IOC’ determines the execution price.

For example, a limit buy at Rs 100 with DAY validity can sit in the book until matched or the day ends. A limit buy at Rs 100 with IOC validity attempts to match immediately at eligible prices and cancels any remainder that cannot be filled at that moment.

How a DAY order works

NSE describes a DAY order as valid for the day on which it is entered. If it is not matched during the day, the system cancels it automatically at the end of the trading day.

The practical benefit is patience: the order can participate in the queue as market conditions evolve. The trade-off is that the order remains exposed to changing information and may fill later when the market context is different from the moment it was placed.

How an IOC order works

An IOC order is released to the market and tries to execute immediately. If only part of the quantity can be matched, that part may trade and the unmatched portion is cancelled immediately. If nothing can be matched, the entire order disappears.

IOC is therefore useful when the trader wants current liquidity but does not want an unfilled balance resting in the book. It is common in execution logic where stale residual orders are undesirable.

Partial fills are the key to understanding IOC

Why a DAY order may not fill even when price touches your level

Orders at the same price are still subject to queue priority. If substantial quantity was already ahead of you, other orders may trade at your price while yours remains unfilled. A brief touch at the limit price is not a guarantee of execution.

This connects directly with BC-026: market depth and price-time priority explain why two investors using the same price can receive different fills.

When IOC can help – and when it can hurt

IOC can help when the main goal is immediate execution against currently displayed liquidity without leaving a residual order. It can also be useful for large or algorithmic execution that repeatedly probes available liquidity.

But IOC can hurt when the security is thinly traded or the investor actually has time to wait. Repeated IOC attempts can create fragmented fills, higher operational complexity and missed execution if liquidity appears seconds later.

What about GTC, GTD and broker-specific choices?

NSE’s equity-market documentation describes Good Till Cancelled and Good Till Date/Days concepts, but also notes that GTC and GTD are currently not available on the exchange system under the cited framework. Retail brokers may present their own ‘good till triggered’ or persistent-order facilities by re-entering instructions under broker-specific terms.

That is why investors should distinguish an exchange-native order validity from a broker service that recreates an instruction on later sessions. The cancellation, trigger and corporate-action rules can differ.

Tradient order-validity checklist

1. Decide whether immediacy or patience matters more.
2. Choose the price instruction separately: market, limit or stop-based.
3. Check likely liquidity and whether partial fills are acceptable.
4. For IOC, assume the unmatched balance can disappear immediately.
5. For DAY, review resting orders if the information or thesis changes.
6. Confirm the exact validity options and broker implementation before submitting.

Key Takeaways

• DAY and IOC are time conditions, not price conditions.
• A DAY order can wait during the session; IOC tries immediately and cancels any remainder.
• IOC permits partial fills.
• Queue priority still matters for DAY orders at a given price.
• Broker labels can differ, so always check whether a persistent order is exchange-native or broker-managed.

FAQs

Is IOC the same as a market order?

No. IOC describes how long the order survives; market describes the price instruction. An IOC order can also be used with a limit price depending on the permitted order entry setup.

Can an IOC order be partially filled?

Yes. NSE states that partial matching is possible and the unmatched portion is cancelled immediately.

Does a DAY order carry to the next trading session?

No. An unmatched DAY order is cancelled at the end of the trading day.

Why did my DAY order not execute even though the price traded there?

Earlier orders may have had queue priority, the trade may have occurred before your order reached the book, or available quantity may have been insufficient.