Lot steps and the partial close that can't happen

[Shadow Trader]

A position of 0.03 lots can't be closed in half. The minimum step is 0.01, so the choices are 0.01 and 0.02, or 0.02 and 0.01.

For a scalper who scales out of trades, step size limits the plan. A strategy that expects to close 50 percent at the first target and the rest at the second needs a position size that divides cleanly.

Some brokers have steps of 0.1, which makes the problem worse. A 0.2 lot position can only be closed all at once or in one piece of 0.1.

Rounding adds more trouble. A script that calculates 0.015 lots might round to 0.01 or 0.02, depending on the code, changing the risk by a third.

The minimum lot and the step should be read from the spec before the position sizing is designed. For small accounts, this decides whether scaling out is even possible.

Some brokers offer cent accounts or micro lots with smaller steps, which allow finer control, usually at a cost in spread or commission.

A neat workaround for small accounts is to design entries in units of the smallest step, and exit plans around that. A position of 0.04 lots can be closed in two parts of 0.02, or in four parts of 0.01. Starting at 0.05 limits clean splits to uneven ones. Choosing the size to match the exit plan, and not the other way around, avoids the rounding trap.

It also pays to check how the platform behaves when a close request is smaller than the minimum step. Some quietly round up and close the entire position, which defeats the purpose and can be an unpleasant surprise.

Does the position sizing here account for the lot step, or does the broker's rounding decide the final size?