MT5 error 10014: how to diagnose invalid volume

When MT5 reports invalid volume, begin with the requested lot size and the symbol specification. Changing an unrelated signal setting will not explain a volume that the server refuses.

Confirm the exact return code

The trade-server code 10014 is TRADE_RETCODE_INVALID_VOLUME. Record it together with the requested volume and symbol. Keep the server return code separate from GetLastError, which reports a different class of program or runtime error. A journal line saying trade failed is too vague to guide a precise fix.

Check the volume grid

Read SYMBOL_VOLUME_MIN, SYMBOL_VOLUME_MAX and SYMBOL_VOLUME_STEP. As an illustration, if the minimum and step are both 0.01, a requested 0.015 lots does not sit on that grid. Check the current symbol rather than assuming every broker or instrument accepts the same lot increment.

Make sizing and rounding explicit

Calculate the intended size, align it to an accepted increment and verify the bounds. If rounding down falls below the minimum, decide explicitly whether the strategy should skip the entry. Automatically rounding up can exceed the original sizing intention. Also inspect any aggregate directional volume limit separately.

Test the full request

1. Log the raw and aligned volume.
2. Check the request with OrderCheck and inspect its result fields.
3. Submit only a valid request in the intended test environment.
4. Inspect the actual server result; a pre-check does not guarantee execution.

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Editable source makes this diagnosis concrete: you can follow the sizing calculation all the way to the request. See My AI Gold MT5 and keep your custom calculations easy to inspect.

Sources and further reading

• Trade server return codes
• OrderCheck
• Symbol properties

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