Why Was My Stock Order Only Partially Filled?

A stock order is partially filled when only part of the requested quantity finds executable shares under your order's price and other instructions. If you submit a limit order to buy 1,000 shares at $25.00 and sellers offer only 600 shares at or below that price, you buy 600, and the other 400 keep working as an open order until they fill, you cancel them, or the order expires. A partial fill is normal market mechanics, not a broker error. What matters next is the remainder, and its fate depends on the time in force, the session, and any conditions attached to the order.

Your order can only take the shares that exist at your price

A limit order sets the worst price you will accept, not the quantity you are guaranteed to receive, a distinction the SEC's investor guide to order types makes explicitly. When a marketable buy limit arrives, it takes the offers priced at or below the limit, starting with the cheapest. Once those offers are used up, execution stops, and the unfilled shares rest on the book as a bid at your limit. A sell limit works the same way in reverse against bids.

The quote on your screen is the first clue, and it is often misread. Fidelity's order-placement FAQ notes that equity bid and ask sizes on its platform are shown in hundreds, so an ask size of 4 means 400 shares, and that a buy order larger than the size at the ask should expect part of it to execute above the ask. With a limit in place, that part does not execute at a worse price. It waits.

A resting balance then fills only as sellers arrive, and it competes with every other bid at the same price. Exchanges rank orders by price first and then by time, so orders that were there before yours absorb incoming volume first, and a single 300-share trade can leave you with 100 shares or none. The queue, the venue split, and the chart "touch" are covered in detail in hi2morrow's guide to why a limit order may not fill after the price touched it.

Market orders in liquid stocks rarely end partially filled during regular hours, because they keep taking offers at progressively worse prices until the quantity is complete. The cost then shows up in the average price rather than in the share count, which is the subject of hi2morrow's guide to why a stock order gets a bad fill. In a thin stock, still read the order status instead of assuming the whole quantity went through.

What happens to the unfilled remainder

The shares already executed are final trades. The rest of the order keeps its original instructions: the same limit price, the same side, and the same time in force. Fidelity's order-type documentation, for example, says that a limit order for several round lots may be filled completely or in part until completed, and that filling it can take more than one trading day unless the order is restricted otherwise.

The time in force decides how long the balance survives. A day order that is only partly executed is canceled at the end of its session, so you keep the shares you bought and lose the rest of the instruction. A good 'til canceled order carries the balance into later sessions until it fills, you cancel it, or it reaches the broker's maximum duration. Orders entered for an extended-hours session usually expire when that session ends, regardless of how much was filled.

On an exchange book that ranks by time, a partial execution does not cost the balance its place in line. Changing the order is a different matter. Under Nasdaq's book-priority rule, Rule 4757, almost any modification other than reducing the size gives the order a new timestamp, so raising the quantity or moving the price sends the remainder to the back of the queue.

Cancellation has a timing issue of its own. A cancel request travels to the venue while the order is still live, and shares can execute before it arrives. Fidelity warns that a cancellation confirmation does not necessarily mean the original order was canceled. After canceling a partly filled order, check the executions before entering a replacement, or you can end up with more shares than you intended.

Order instructions that allow, prevent, or limit partial fills

The default for most orders is to accept partial executions. FINRA's guide to time parameters and order qualifiers describes the instructions that change that behavior, and they are worth knowing before the order goes in rather than after:

1. A day order can fill in pieces through the session, and any balance expires when the session closes.
2. A good 'til canceled order can fill in pieces over several days until it is complete, canceled, or reaches the broker's time limit.
3. An immediate-or-cancel order takes whatever is available at your price right away and cancels the rest, so a partial fill is the expected outcome.
4. A fill-or-kill order executes the entire quantity immediately or not at all.
5. An all-or-none order also refuses partial fills, but without the immediacy: it waits until a counterparty for the full quantity appears, or until it is canceled or expires.

All-or-none swaps one problem for another. Fidelity describes it as a restricted order: the stock may trade at your price without your order having any right to execute unless the entire quantity is available. You avoid an awkward 300-share position, but you accept a higher chance of getting nothing. Availability is also a matter of broker policy. Fidelity, for instance, accepts fill-or-kill only for 100 shares or more, only during market hours, and only as a day order, and many brokers do not offer these conditions in extended hours at all.

A worked example: 1,000 shares of ABC at $25.00

On a Monday at 10:02 a.m. ET, ABC is bid $24.96 and offered at $24.98 for 400 shares. Behind the inside offer sit 200 shares at $25.00 and 900 at $25.03. A trader enters a limit order to buy 1,000 shares at $25.00.

The order immediately takes 400 shares at $24.98 and 200 at $25.00. The next offer, at $25.03, is above the limit, so execution stops at 600 shares. The remaining 400 shares post as a bid at $25.00, which is now the best bid. Over the rest of the day, sellers hit that bid for another 150 shares. By the close, the trader owns 750 shares at an average of $24.9893: $9,992 for the first 400 and $8,750 for the next 350, divided by 750.

If the order was a day order, the last 250 shares are canceled at 4:00 p.m. and the position is simply 750 shares. If it was good 'til canceled, the 250-share balance returns on Tuesday, and suppose a seller hits it at 9:47 a.m. at $25.00. The position becomes 1,000 shares at an average of $24.992, but it was built on two trade dates. Under the T+1 cycle described in FINRA's guide to settlement cycles, Monday's 750 shares settle on Tuesday and Tuesday's 250 settle on Wednesday. At a broker that still charges commissions on the trade, the multi-day fill can also cost more: Fidelity's FAQ, for example, assesses one commission for each day on which a good 'til canceled order receives executions.

The risk side matters more than the accounting. If the plan was a protective stop at $24.50 on 1,000 shares, the real position on Monday evening is 750 shares, and the stop should be sized to 750. A sell stop for 1,000 shares against a 750-share position would, depending on the account, either be rejected or try to sell 250 shares the trader does not own. Measured from the actual average, the Monday risk to $24.50 is about $367 rather than the planned $500.

Sessions, odd lots, short sales, and halts

Extended hours produce partial fills far more often than the regular session. Liquidity is thinner, brokers generally accept only limit orders, and Fidelity notes that conditions outside regular hours can keep an order from executing in whole or in part, with the unfilled portion canceled when the session ends. Broker windows and routing differ, as hi2morrow's guide to why premarket orders do not fill explains.

Odd lots are the next wrinkle, and the definition itself has changed. A round lot is no longer always 100 shares. Since November 3, 2025, the SEC's tiered definition sets it at 100 shares for stocks averaging up to $250, 40 shares up to $1,000, 10 shares up to $10,000, and 1 share above that, as summarized in NYSE's round-lot regulatory memo. A partial fill often leaves an odd-lot balance, such as 37 shares of a $60 stock. That balance can still execute, but odd-lot interest does not set the national best bid or offer, so your remaining bid may not show up as the inside quote even when it is the best price on the book.

Short sales add a regulatory step. A broker must locate shares to borrow before each short sale and on the same day it is effected. The SEC's Regulation SHO staff FAQ states that a good 'til canceled short order not executed on the day of the locate needs a new one. If a short order fills partially on Monday and the stock becomes hard to borrow overnight, the Tuesday balance may be rejected or canceled even though the order itself never changed.

A trading halt or a limit up-limit down pause stops executions entirely, and the stock may reopen well away from your limit, leaving the balance either filled at once or stranded far from the market.

Deciding what to do with the rest

A partial fill leaves three reasonable choices: let the balance keep working, reprice it, or cancel it. Leaving it is right when the original price still reflects the trade you want. Repricing buys a higher chance of completion at the cost of the price you chose and, on most venues, your place in line. Canceling turns the partial fill into the final size, which is often the cleanest decision when the stock has moved away from your level.

Whatever you choose, work from the broker's record rather than the order ticket. Confirm the executed quantity and the average price, check which shares are still open, and resize everything that depends on the position, including stops, profit targets, and the legs of any bracket or one-cancels-other order, rather than assuming they adjusted on their own.

Alexander Styopin's professional view: a partial fill is information, not an inconvenience. The market has told you how much stock was available at your price at that moment. Chasing the last 25% of an order by lifting the offer usually costs more on those final shares than the limit saved on the first ones, and it turns a planned entry into an emotional one. In practice, the better habit is to decide before entry whether the trade still works at half or three-quarters of the intended size. If it does, a partial fill is an acceptable outcome. If it does not, the order was too large for the liquidity at that level, and the answer is a smaller order or a different price, not a chase.

Educational material only. Not investment or legal advice. Order handling, time-in-force options, extended-hours access, commissions, and settlement practices vary by broker, market center, security, and account type.

Author: Alexander Styopin, hi2morrow analyst and economist with 25 years of experience in the US stock market