Partial Fills & Copying

A partial fill is when an order fills in stages — say you send a 5-lot on ES and it comes back as a 2-lot, then a 1-lot, then a final 2-lot before the order is fully filled. Partials are normal in futures, especially on larger orders or in thinner books. This article explains precisely how MimikTrader copies a leader order that fills in pieces.

Why Partials Happen

When you send an order for more contracts than are available at one price, the exchange fills what it can and keeps working the rest. Each chunk that fills is a partial fill; the order is only fully filled once the whole quantity has traded. Between those events the order is still working, with some quantity done and some remaining.

Market Copies Fire Once, at the Full Fill

For a follower copying on a market basis, MimikTrader places the follower’s order once per leader order, and only when the leader’s order reaches its complete, final fill. Partials along the way are held — they do not trigger their own copies. The follower does not receive one small order per partial and then more orders as the rest fills.

Example

The leader sends a 5-lot on MNQ, and it fills as 1 + 3 + 1 across a few moments. During the first two partials, the followers place nothing. When that final 1-lot completes the leader’s order, each follower places exactly one order.

Sized to the Full Order, Not the Pieces

The follower’s single order is sized to the leader’s full original order quantity— not the size of any one partial, and not a running total that changes as partials arrive. The follower’s multiplier is applied to that full quantity.

Continuing the example above, a follower on a 1.0 multiplier copies the full 5-lot as a single 5-lot once the leader’s order completes. A follower on a 0.5 multiplier copies ceil(5 × 0.5) = 3 contracts. In both cases the sizing is against the leader’s full 5-lot order, regardless of how many partials it took to fill. See Position Sizing for the full multiplier formula and rounding rule.

Working Limit and Stop Entries Mirror at Submission

The “wait for the full fill” behavior above applies to market-style copying. A follower configured to mirror working entriesinstead — copying the leader’s resting limit or stop orders — receives its copy at the moment the leader submits that working order, rather than waiting for a fill. In that mode the follower has its own working entry sitting in the market alongside the leader’s, and it fills on its own terms.

If the Leader Cancels the Remainder

Because a market copy only fires at the leader’s complete fill, a leader order that never reaches a complete fill never produces a market copy. So if the leader takes a partial fill and then cancels the unfilled remainder of a market order, the followers receive no market copy for that order at all — the order never reached the terminal full fill that would have triggered one, and there is no catch-up or after-the-fact copy.

The working-entry case is different. If the leader had a working limit or stop entry that was already mirrored to a follower, and the leader cancels that working order, the follower’s still-resting entry order is cancelled too— the mirrored working entry is pulled back along with the leader’s.

Your Own Order Can Partial-Fill Too

Everything above describes how the leader’sfills drive the copy. Once a follower’s own order is placed, it is a real order on that follower’s broker account and is subject to that account’s own liquidity. A follower’s order can itself partial-fill against the book it is trading into, just like any order you place manually. That is a normal property of the follower’s market, separate from how the copy was triggered.

Quick Summary

• Market copies fire once, only when the leader’s order fully fills.
• Partials along the way are held — no per-partial follower orders.
• The follower order is sized to the leader’s full order quantity × the multiplier.
• Working limit/stop entries mirror at submission instead of waiting for a fill.
• If the leader cancels the remainder, followers get no market copy; a mirrored working entry is cancelled.
• A follower’s own order can still partial-fill against its own liquidity.