How should automated trading handle partial fills?

What this means in practice

Requested volume and actually filled volume are separate states. Risk controls, remaining orders and exits should use the real filled/current position volume, not assume the original request filled completely. This page is specifically about “How should automated trading handle partial fills?”, so each scenario below is explained by its own mechanism instead of sharing one generic diagnosis.

Real-world scenarios

Scenario A — Partial entry fill

Use actual current position volume as the source of truth. A partial close must specify which position to reduce and by how much; later risk and protection should use the remaining cTrader volume. For Scenario A — Partial entry fill on question 89, use that evidence specifically to answer “How should automated trading handle partial fills?”; keep it separate from the evidence for the other scenarios on this page.

Scenario B — Partial exit

Use actual current position volume as the source of truth. A partial close must specify which position to reduce and by how much; later risk and protection should use the remaining cTrader volume. For Scenario B — Partial exit on question 89, use that evidence specifically to answer “How should automated trading handle partial fills?”; keep it separate from the evidence for the other scenarios on this page.

Scenario C — Remaining protection

Use actual current position volume as the source of truth. A partial close must specify which position to reduce and by how much; later risk and protection should use the remaining cTrader volume. For Scenario C — Remaining protection on question 89, use that evidence specifically to answer “How should automated trading handle partial fills?”; keep it separate from the evidence for the other scenarios on this page.

What to check

• intended signal/action
• last stage that definitely succeeded
• first stage that differs from intent
• final cTrader state after the event

Practical rule

For “How should automated trading handle partial fills?”, change only the first layer whose evidence no longer matches the intended action. Preserve signal identity, timestamps and final cTrader state, and reproduce execution-affecting changes on demo before live use.