Partial Fills
Definition
A partial fill occurs when only some of an order's quantity executes, because the book at the order's price held less than the full size. What happens to the remainder depends on the order type: it can keep resting in the book, be cancelled immediately, or, for an all-or-nothing order, prevent any fill at all. Polymarket notes that limit orders 'can partially fill as different traders match portions of your order.'
Why it matters
Partial fills are normal in thin markets and can quietly change a plan: a smaller position than intended, a remainder that fills later at a stale price, or a one-sided hedge. Investors should check fills after every order, cancel or adjust remainders deliberately, and use fill-or-kill when only the full size makes sense.
Common misconceptions
- •An order showing as placed is not necessarily filled.
- •A resting remainder can fill later, after the market has moved.
- •Fees are charged on what fills, not on what was ordered.
- •The label is only a starting point. Investor outcomes usually depend on the governing documents, cash-flow priority, valuation policy, disclosure quality, and manager discretion surrounding the term, not just the shorthand definition used in marketing materials.
Technical details
Tracking an order
Filled quantity and average price: the position.
Remaining quantity: still resting, cancelled, or expired.
Funds committed to the remainder until it is cancelled.
Fees on each fill.
How investors apply the term
Investors usually apply this term by tying the definition back to the controlling documents and then asking which cash flows, rights, restrictions, or valuation assumptions it changes. A useful review looks at the term alongside fees, leverage, liquidity, reporting frequency, and manager discretion rather than treating it as a standalone concept.
The practical diligence test is simple: identify who benefits if the assumption is wrong, who has control when conditions change, and what evidence the investor receives after closing. Terms that cannot be reconciled to documents, cash movements, and monitoring data should be treated as marketing shorthand until proven otherwise.
Frequently asked questions
- What happens when only part of my event-contract order fills?
- You hold the filled contracts as a position, and the rest follows the order type. On Polymarket a good-till-cancelled order keeps the remainder resting; a fill-and-kill order 'fills what's available' and cancels the rest; a fill-or-kill order fills entirely or is cancelled, so it never partially fills.
- Is my money tied up by the unfilled part?
- Usually, while it rests. Polymarket validates that 'you have sufficient balance' before accepting an order, so funds for a resting order are committed to it. Cancelling the remainder releases them.
- Why does a partial fill matter?
- It can leave a position of the wrong size. A trader building a hedge or an offsetting pair may end up with one leg filled and the other not, exposed to the full risk of the filled leg until they act.